chore: blacken (#375)

diff --git a/tests/test_jwt.py b/tests/test_jwt.py
index 4a64717..b0c6e48 100644
--- a/tests/test_jwt.py
+++ b/tests/test_jwt.py
@@ -26,41 +26,45 @@
 from google.auth import jwt
 
 
-DATA_DIR = os.path.join(os.path.dirname(__file__), 'data')
+DATA_DIR = os.path.join(os.path.dirname(__file__), "data")
 
-with open(os.path.join(DATA_DIR, 'privatekey.pem'), 'rb') as fh:
+with open(os.path.join(DATA_DIR, "privatekey.pem"), "rb") as fh:
     PRIVATE_KEY_BYTES = fh.read()
 
-with open(os.path.join(DATA_DIR, 'public_cert.pem'), 'rb') as fh:
+with open(os.path.join(DATA_DIR, "public_cert.pem"), "rb") as fh:
     PUBLIC_CERT_BYTES = fh.read()
 
-with open(os.path.join(DATA_DIR, 'other_cert.pem'), 'rb') as fh:
+with open(os.path.join(DATA_DIR, "other_cert.pem"), "rb") as fh:
     OTHER_CERT_BYTES = fh.read()
 
-SERVICE_ACCOUNT_JSON_FILE = os.path.join(DATA_DIR, 'service_account.json')
+SERVICE_ACCOUNT_JSON_FILE = os.path.join(DATA_DIR, "service_account.json")
 
-with open(SERVICE_ACCOUNT_JSON_FILE, 'r') as fh:
+with open(SERVICE_ACCOUNT_JSON_FILE, "r") as fh:
     SERVICE_ACCOUNT_INFO = json.load(fh)
 
 
 @pytest.fixture
 def signer():
-    return crypt.RSASigner.from_string(PRIVATE_KEY_BYTES, '1')
+    return crypt.RSASigner.from_string(PRIVATE_KEY_BYTES, "1")
 
 
 def test_encode_basic(signer):
-    test_payload = {'test': 'value'}
+    test_payload = {"test": "value"}
     encoded = jwt.encode(signer, test_payload)
     header, payload, _, _ = jwt._unverified_decode(encoded)
     assert payload == test_payload
-    assert header == {'typ': 'JWT', 'alg': 'RS256', 'kid': signer.key_id}
+    assert header == {"typ": "JWT", "alg": "RS256", "kid": signer.key_id}
 
 
 def test_encode_extra_headers(signer):
-    encoded = jwt.encode(signer, {}, header={'extra': 'value'})
+    encoded = jwt.encode(signer, {}, header={"extra": "value"})
     header = jwt.decode_header(encoded)
     assert header == {
-        'typ': 'JWT', 'alg': 'RS256', 'kid': signer.key_id, 'extra': 'value'}
+        "typ": "JWT",
+        "alg": "RS256",
+        "kid": signer.key_id,
+        "extra": "value",
+    }
 
 
 @pytest.fixture
@@ -68,11 +72,11 @@
     def factory(claims=None, key_id=None):
         now = _helpers.datetime_to_secs(_helpers.utcnow())
         payload = {
-            'aud': 'audience@example.com',
-            'iat': now,
-            'exp': now + 300,
-            'user': 'billy bob',
-            'metadata': {'meta': 'data'}
+            "aud": "audience@example.com",
+            "iat": now,
+            "exp": now + 300,
+            "user": "billy bob",
+            "metadata": {"meta": "data"},
         }
         payload.update(claims or {})
 
@@ -83,154 +87,168 @@
             key_id = None
 
         return jwt.encode(signer, payload, key_id=key_id)
+
     return factory
 
 
 def test_decode_valid(token_factory):
     payload = jwt.decode(token_factory(), certs=PUBLIC_CERT_BYTES)
-    assert payload['aud'] == 'audience@example.com'
-    assert payload['user'] == 'billy bob'
-    assert payload['metadata']['meta'] == 'data'
+    assert payload["aud"] == "audience@example.com"
+    assert payload["user"] == "billy bob"
+    assert payload["metadata"]["meta"] == "data"
 
 
 def test_decode_valid_with_audience(token_factory):
     payload = jwt.decode(
-        token_factory(), certs=PUBLIC_CERT_BYTES,
-        audience='audience@example.com')
-    assert payload['aud'] == 'audience@example.com'
-    assert payload['user'] == 'billy bob'
-    assert payload['metadata']['meta'] == 'data'
+        token_factory(), certs=PUBLIC_CERT_BYTES, audience="audience@example.com"
+    )
+    assert payload["aud"] == "audience@example.com"
+    assert payload["user"] == "billy bob"
+    assert payload["metadata"]["meta"] == "data"
 
 
 def test_decode_valid_unverified(token_factory):
     payload = jwt.decode(token_factory(), certs=OTHER_CERT_BYTES, verify=False)
-    assert payload['aud'] == 'audience@example.com'
-    assert payload['user'] == 'billy bob'
-    assert payload['metadata']['meta'] == 'data'
+    assert payload["aud"] == "audience@example.com"
+    assert payload["user"] == "billy bob"
+    assert payload["metadata"]["meta"] == "data"
 
 
 def test_decode_bad_token_wrong_number_of_segments():
     with pytest.raises(ValueError) as excinfo:
-        jwt.decode('1.2', PUBLIC_CERT_BYTES)
-    assert excinfo.match(r'Wrong number of segments')
+        jwt.decode("1.2", PUBLIC_CERT_BYTES)
+    assert excinfo.match(r"Wrong number of segments")
 
 
 def test_decode_bad_token_not_base64():
     with pytest.raises((ValueError, TypeError)) as excinfo:
-        jwt.decode('1.2.3', PUBLIC_CERT_BYTES)
-    assert excinfo.match(r'Incorrect padding|more than a multiple of 4')
+        jwt.decode("1.2.3", PUBLIC_CERT_BYTES)
+    assert excinfo.match(r"Incorrect padding|more than a multiple of 4")
 
 
 def test_decode_bad_token_not_json():
-    token = b'.'.join([base64.urlsafe_b64encode(b'123!')] * 3)
+    token = b".".join([base64.urlsafe_b64encode(b"123!")] * 3)
     with pytest.raises(ValueError) as excinfo:
         jwt.decode(token, PUBLIC_CERT_BYTES)
-    assert excinfo.match(r'Can\'t parse segment')
+    assert excinfo.match(r"Can\'t parse segment")
 
 
 def test_decode_bad_token_no_iat_or_exp(signer):
-    token = jwt.encode(signer, {'test': 'value'})
+    token = jwt.encode(signer, {"test": "value"})
     with pytest.raises(ValueError) as excinfo:
         jwt.decode(token, PUBLIC_CERT_BYTES)
-    assert excinfo.match(r'Token does not contain required claim')
+    assert excinfo.match(r"Token does not contain required claim")
 
 
 def test_decode_bad_token_too_early(token_factory):
-    token = token_factory(claims={
-        'iat': _helpers.datetime_to_secs(
-            _helpers.utcnow() + datetime.timedelta(hours=1))
-    })
+    token = token_factory(
+        claims={
+            "iat": _helpers.datetime_to_secs(
+                _helpers.utcnow() + datetime.timedelta(hours=1)
+            )
+        }
+    )
     with pytest.raises(ValueError) as excinfo:
         jwt.decode(token, PUBLIC_CERT_BYTES)
-    assert excinfo.match(r'Token used too early')
+    assert excinfo.match(r"Token used too early")
 
 
 def test_decode_bad_token_expired(token_factory):
-    token = token_factory(claims={
-        'exp': _helpers.datetime_to_secs(
-            _helpers.utcnow() - datetime.timedelta(hours=1))
-    })
+    token = token_factory(
+        claims={
+            "exp": _helpers.datetime_to_secs(
+                _helpers.utcnow() - datetime.timedelta(hours=1)
+            )
+        }
+    )
     with pytest.raises(ValueError) as excinfo:
         jwt.decode(token, PUBLIC_CERT_BYTES)
-    assert excinfo.match(r'Token expired')
+    assert excinfo.match(r"Token expired")
 
 
 def test_decode_bad_token_wrong_audience(token_factory):
     token = token_factory()
-    audience = 'audience2@example.com'
+    audience = "audience2@example.com"
     with pytest.raises(ValueError) as excinfo:
         jwt.decode(token, PUBLIC_CERT_BYTES, audience=audience)
-    assert excinfo.match(r'Token has wrong audience')
+    assert excinfo.match(r"Token has wrong audience")
 
 
 def test_decode_wrong_cert(token_factory):
     with pytest.raises(ValueError) as excinfo:
         jwt.decode(token_factory(), OTHER_CERT_BYTES)
-    assert excinfo.match(r'Could not verify token signature')
+    assert excinfo.match(r"Could not verify token signature")
 
 
 def test_decode_multicert_bad_cert(token_factory):
-    certs = {'1': OTHER_CERT_BYTES, '2': PUBLIC_CERT_BYTES}
+    certs = {"1": OTHER_CERT_BYTES, "2": PUBLIC_CERT_BYTES}
     with pytest.raises(ValueError) as excinfo:
         jwt.decode(token_factory(), certs)
-    assert excinfo.match(r'Could not verify token signature')
+    assert excinfo.match(r"Could not verify token signature")
 
 
 def test_decode_no_cert(token_factory):
-    certs = {'2': PUBLIC_CERT_BYTES}
+    certs = {"2": PUBLIC_CERT_BYTES}
     with pytest.raises(ValueError) as excinfo:
         jwt.decode(token_factory(), certs)
-    assert excinfo.match(r'Certificate for key id 1 not found')
+    assert excinfo.match(r"Certificate for key id 1 not found")
 
 
 def test_decode_no_key_id(token_factory):
     token = token_factory(key_id=False)
-    certs = {'2': PUBLIC_CERT_BYTES}
+    certs = {"2": PUBLIC_CERT_BYTES}
     payload = jwt.decode(token, certs)
-    assert payload['user'] == 'billy bob'
+    assert payload["user"] == "billy bob"
 
 
 def test_roundtrip_explicit_key_id(token_factory):
-    token = token_factory(key_id='3')
-    certs = {'2': OTHER_CERT_BYTES, '3': PUBLIC_CERT_BYTES}
+    token = token_factory(key_id="3")
+    certs = {"2": OTHER_CERT_BYTES, "3": PUBLIC_CERT_BYTES}
     payload = jwt.decode(token, certs)
-    assert payload['user'] == 'billy bob'
+    assert payload["user"] == "billy bob"
 
 
 class TestCredentials(object):
-    SERVICE_ACCOUNT_EMAIL = 'service-account@example.com'
-    SUBJECT = 'subject'
-    AUDIENCE = 'audience'
-    ADDITIONAL_CLAIMS = {'meta': 'data'}
+    SERVICE_ACCOUNT_EMAIL = "service-account@example.com"
+    SUBJECT = "subject"
+    AUDIENCE = "audience"
+    ADDITIONAL_CLAIMS = {"meta": "data"}
     credentials = None
 
     @pytest.fixture(autouse=True)
     def credentials_fixture(self, signer):
         self.credentials = jwt.Credentials(
-            signer, self.SERVICE_ACCOUNT_EMAIL, self.SERVICE_ACCOUNT_EMAIL,
-            self.AUDIENCE)
+            signer,
+            self.SERVICE_ACCOUNT_EMAIL,
+            self.SERVICE_ACCOUNT_EMAIL,
+            self.AUDIENCE,
+        )
 
     def test_from_service_account_info(self):
-        with open(SERVICE_ACCOUNT_JSON_FILE, 'r') as fh:
+        with open(SERVICE_ACCOUNT_JSON_FILE, "r") as fh:
             info = json.load(fh)
 
         credentials = jwt.Credentials.from_service_account_info(
-            info, audience=self.AUDIENCE)
+            info, audience=self.AUDIENCE
+        )
 
-        assert credentials._signer.key_id == info['private_key_id']
-        assert credentials._issuer == info['client_email']
-        assert credentials._subject == info['client_email']
+        assert credentials._signer.key_id == info["private_key_id"]
+        assert credentials._issuer == info["client_email"]
+        assert credentials._subject == info["client_email"]
         assert credentials._audience == self.AUDIENCE
 
     def test_from_service_account_info_args(self):
         info = SERVICE_ACCOUNT_INFO.copy()
 
         credentials = jwt.Credentials.from_service_account_info(
-            info, subject=self.SUBJECT, audience=self.AUDIENCE,
-            additional_claims=self.ADDITIONAL_CLAIMS)
+            info,
+            subject=self.SUBJECT,
+            audience=self.AUDIENCE,
+            additional_claims=self.ADDITIONAL_CLAIMS,
+        )
 
-        assert credentials._signer.key_id == info['private_key_id']
-        assert credentials._issuer == info['client_email']
+        assert credentials._signer.key_id == info["private_key_id"]
+        assert credentials._issuer == info["client_email"]
         assert credentials._subject == self.SUBJECT
         assert credentials._audience == self.AUDIENCE
         assert credentials._additional_claims == self.ADDITIONAL_CLAIMS
@@ -239,33 +257,37 @@
         info = SERVICE_ACCOUNT_INFO.copy()
 
         credentials = jwt.Credentials.from_service_account_file(
-            SERVICE_ACCOUNT_JSON_FILE, audience=self.AUDIENCE)
+            SERVICE_ACCOUNT_JSON_FILE, audience=self.AUDIENCE
+        )
 
-        assert credentials._signer.key_id == info['private_key_id']
-        assert credentials._issuer == info['client_email']
-        assert credentials._subject == info['client_email']
+        assert credentials._signer.key_id == info["private_key_id"]
+        assert credentials._issuer == info["client_email"]
+        assert credentials._subject == info["client_email"]
         assert credentials._audience == self.AUDIENCE
 
     def test_from_service_account_file_args(self):
         info = SERVICE_ACCOUNT_INFO.copy()
 
         credentials = jwt.Credentials.from_service_account_file(
-            SERVICE_ACCOUNT_JSON_FILE, subject=self.SUBJECT,
-            audience=self.AUDIENCE, additional_claims=self.ADDITIONAL_CLAIMS)
+            SERVICE_ACCOUNT_JSON_FILE,
+            subject=self.SUBJECT,
+            audience=self.AUDIENCE,
+            additional_claims=self.ADDITIONAL_CLAIMS,
+        )
 
-        assert credentials._signer.key_id == info['private_key_id']
-        assert credentials._issuer == info['client_email']
+        assert credentials._signer.key_id == info["private_key_id"]
+        assert credentials._issuer == info["client_email"]
         assert credentials._subject == self.SUBJECT
         assert credentials._audience == self.AUDIENCE
         assert credentials._additional_claims == self.ADDITIONAL_CLAIMS
 
     def test_from_signing_credentials(self):
         jwt_from_signing = self.credentials.from_signing_credentials(
-            self.credentials,
-            audience=mock.sentinel.new_audience)
+            self.credentials, audience=mock.sentinel.new_audience
+        )
         jwt_from_info = jwt.Credentials.from_service_account_info(
-            SERVICE_ACCOUNT_INFO,
-            audience=mock.sentinel.new_audience)
+            SERVICE_ACCOUNT_INFO, audience=mock.sentinel.new_audience
+        )
 
         assert isinstance(jwt_from_signing, jwt.Credentials)
         assert jwt_from_signing._signer.key_id == jwt_from_info._signer.key_id
@@ -279,19 +301,17 @@
         assert not self.credentials.expired
 
     def test_with_claims(self):
-        new_audience = 'new_audience'
-        new_credentials = self.credentials.with_claims(
-            audience=new_audience)
+        new_audience = "new_audience"
+        new_credentials = self.credentials.with_claims(audience=new_audience)
 
         assert new_credentials._signer == self.credentials._signer
         assert new_credentials._issuer == self.credentials._issuer
         assert new_credentials._subject == self.credentials._subject
         assert new_credentials._audience == new_audience
-        assert (new_credentials._additional_claims ==
-                self.credentials._additional_claims)
+        assert new_credentials._additional_claims == self.credentials._additional_claims
 
     def test_sign_bytes(self):
-        to_sign = b'123'
+        to_sign = b"123"
         signature = self.credentials.sign_bytes(to_sign)
         assert crypt.verify_signature(to_sign, signature, PUBLIC_CERT_BYTES)
 
@@ -299,12 +319,11 @@
         assert isinstance(self.credentials.signer, crypt.RSASigner)
 
     def test_signer_email(self):
-        assert (self.credentials.signer_email ==
-                SERVICE_ACCOUNT_INFO['client_email'])
+        assert self.credentials.signer_email == SERVICE_ACCOUNT_INFO["client_email"]
 
     def _verify_token(self, token):
         payload = jwt.decode(token, PUBLIC_CERT_BYTES)
-        assert payload['iss'] == self.SERVICE_ACCOUNT_EMAIL
+        assert payload["iss"] == self.SERVICE_ACCOUNT_EMAIL
         return payload
 
     def test_refresh(self):
@@ -318,7 +337,7 @@
         self.credentials.refresh(None)
         assert not self.credentials.expired
 
-        with mock.patch('google.auth._helpers.utcnow') as now:
+        with mock.patch("google.auth._helpers.utcnow") as now:
             one_day = datetime.timedelta(days=1)
             now.return_value = self.credentials.expiry + one_day
             assert self.credentials.expired
@@ -328,55 +347,58 @@
 
         self.credentials.refresh(None)
         self.credentials.before_request(
-            None, 'GET', 'http://example.com?a=1#3', headers)
+            None, "GET", "http://example.com?a=1#3", headers
+        )
 
-        header_value = headers['authorization']
-        _, token = header_value.split(' ')
+        header_value = headers["authorization"]
+        _, token = header_value.split(" ")
 
         # Since the audience is set, it should use the existing token.
-        assert token.encode('utf-8') == self.credentials.token
+        assert token.encode("utf-8") == self.credentials.token
 
         payload = self._verify_token(token)
-        assert payload['aud'] == self.AUDIENCE
+        assert payload["aud"] == self.AUDIENCE
 
     def test_before_request_refreshes(self):
         assert not self.credentials.valid
-        self.credentials.before_request(
-            None, 'GET', 'http://example.com?a=1#3', {})
+        self.credentials.before_request(None, "GET", "http://example.com?a=1#3", {})
         assert self.credentials.valid
 
 
 class TestOnDemandCredentials(object):
-    SERVICE_ACCOUNT_EMAIL = 'service-account@example.com'
-    SUBJECT = 'subject'
-    ADDITIONAL_CLAIMS = {'meta': 'data'}
+    SERVICE_ACCOUNT_EMAIL = "service-account@example.com"
+    SUBJECT = "subject"
+    ADDITIONAL_CLAIMS = {"meta": "data"}
     credentials = None
 
     @pytest.fixture(autouse=True)
     def credentials_fixture(self, signer):
         self.credentials = jwt.OnDemandCredentials(
-            signer, self.SERVICE_ACCOUNT_EMAIL, self.SERVICE_ACCOUNT_EMAIL,
-            max_cache_size=2)
+            signer,
+            self.SERVICE_ACCOUNT_EMAIL,
+            self.SERVICE_ACCOUNT_EMAIL,
+            max_cache_size=2,
+        )
 
     def test_from_service_account_info(self):
-        with open(SERVICE_ACCOUNT_JSON_FILE, 'r') as fh:
+        with open(SERVICE_ACCOUNT_JSON_FILE, "r") as fh:
             info = json.load(fh)
 
         credentials = jwt.OnDemandCredentials.from_service_account_info(info)
 
-        assert credentials._signer.key_id == info['private_key_id']
-        assert credentials._issuer == info['client_email']
-        assert credentials._subject == info['client_email']
+        assert credentials._signer.key_id == info["private_key_id"]
+        assert credentials._issuer == info["client_email"]
+        assert credentials._subject == info["client_email"]
 
     def test_from_service_account_info_args(self):
         info = SERVICE_ACCOUNT_INFO.copy()
 
         credentials = jwt.OnDemandCredentials.from_service_account_info(
-            info, subject=self.SUBJECT,
-            additional_claims=self.ADDITIONAL_CLAIMS)
+            info, subject=self.SUBJECT, additional_claims=self.ADDITIONAL_CLAIMS
+        )
 
-        assert credentials._signer.key_id == info['private_key_id']
-        assert credentials._issuer == info['client_email']
+        assert credentials._signer.key_id == info["private_key_id"]
+        assert credentials._issuer == info["client_email"]
         assert credentials._subject == self.SUBJECT
         assert credentials._additional_claims == self.ADDITIONAL_CLAIMS
 
@@ -384,29 +406,32 @@
         info = SERVICE_ACCOUNT_INFO.copy()
 
         credentials = jwt.OnDemandCredentials.from_service_account_file(
-            SERVICE_ACCOUNT_JSON_FILE)
+            SERVICE_ACCOUNT_JSON_FILE
+        )
 
-        assert credentials._signer.key_id == info['private_key_id']
-        assert credentials._issuer == info['client_email']
-        assert credentials._subject == info['client_email']
+        assert credentials._signer.key_id == info["private_key_id"]
+        assert credentials._issuer == info["client_email"]
+        assert credentials._subject == info["client_email"]
 
     def test_from_service_account_file_args(self):
         info = SERVICE_ACCOUNT_INFO.copy()
 
         credentials = jwt.OnDemandCredentials.from_service_account_file(
-            SERVICE_ACCOUNT_JSON_FILE, subject=self.SUBJECT,
-            additional_claims=self.ADDITIONAL_CLAIMS)
+            SERVICE_ACCOUNT_JSON_FILE,
+            subject=self.SUBJECT,
+            additional_claims=self.ADDITIONAL_CLAIMS,
+        )
 
-        assert credentials._signer.key_id == info['private_key_id']
-        assert credentials._issuer == info['client_email']
+        assert credentials._signer.key_id == info["private_key_id"]
+        assert credentials._issuer == info["client_email"]
         assert credentials._subject == self.SUBJECT
         assert credentials._additional_claims == self.ADDITIONAL_CLAIMS
 
     def test_from_signing_credentials(self):
-        jwt_from_signing = self.credentials.from_signing_credentials(
-            self.credentials)
+        jwt_from_signing = self.credentials.from_signing_credentials(self.credentials)
         jwt_from_info = jwt.OnDemandCredentials.from_service_account_info(
-            SERVICE_ACCOUNT_INFO)
+            SERVICE_ACCOUNT_INFO
+        )
 
         assert isinstance(jwt_from_signing, jwt.OnDemandCredentials)
         assert jwt_from_signing._signer.key_id == jwt_from_info._signer.key_id
@@ -420,9 +445,8 @@
         assert not self.credentials.expired
 
     def test_with_claims(self):
-        new_claims = {'meep': 'moop'}
-        new_credentials = self.credentials.with_claims(
-            additional_claims=new_claims)
+        new_claims = {"meep": "moop"}
+        new_credentials = self.credentials.with_claims(additional_claims=new_claims)
 
         assert new_credentials._signer == self.credentials._signer
         assert new_credentials._issuer == self.credentials._issuer
@@ -430,7 +454,7 @@
         assert new_credentials._additional_claims == new_claims
 
     def test_sign_bytes(self):
-        to_sign = b'123'
+        to_sign = b"123"
         signature = self.credentials.sign_bytes(to_sign)
         assert crypt.verify_signature(to_sign, signature, PUBLIC_CERT_BYTES)
 
@@ -438,12 +462,11 @@
         assert isinstance(self.credentials.signer, crypt.RSASigner)
 
     def test_signer_email(self):
-        assert (self.credentials.signer_email ==
-                SERVICE_ACCOUNT_INFO['client_email'])
+        assert self.credentials.signer_email == SERVICE_ACCOUNT_INFO["client_email"]
 
     def _verify_token(self, token):
         payload = jwt.decode(token, PUBLIC_CERT_BYTES)
-        assert payload['iss'] == self.SERVICE_ACCOUNT_EMAIL
+        assert payload["iss"] == self.SERVICE_ACCOUNT_EMAIL
         return payload
 
     def test_refresh(self):
@@ -454,25 +477,27 @@
         headers = {}
 
         self.credentials.before_request(
-            None, 'GET', 'http://example.com?a=1#3', headers)
+            None, "GET", "http://example.com?a=1#3", headers
+        )
 
-        _, token = headers['authorization'].split(' ')
+        _, token = headers["authorization"].split(" ")
         payload = self._verify_token(token)
 
-        assert payload['aud'] == 'http://example.com'
+        assert payload["aud"] == "http://example.com"
 
         # Making another request should re-use the same token.
-        self.credentials.before_request(
-            None, 'GET', 'http://example.com?b=2', headers)
+        self.credentials.before_request(None, "GET", "http://example.com?b=2", headers)
 
-        _, new_token = headers['authorization'].split(' ')
+        _, new_token = headers["authorization"].split(" ")
 
         assert new_token == token
 
     def test_expired_token(self):
-        self.credentials._cache['audience'] = (
-            mock.sentinel.token, datetime.datetime.min)
+        self.credentials._cache["audience"] = (
+            mock.sentinel.token,
+            datetime.datetime.min,
+        )
 
-        token = self.credentials._get_jwt_for_audience('audience')
+        token = self.credentials._get_jwt_for_audience("audience")
 
         assert token != mock.sentinel.token