tests: drop use of 'unittest2' (#1564)

diff --git a/noxfile.py b/noxfile.py
index 6e2cadc..27a8714 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -27,7 +27,6 @@
     "pytest-cov",
     "webtest",
     "coverage",
-    "unittest2",
     "mock",
 ]
 
diff --git a/tests/test__auth.py b/tests/test__auth.py
index 6347e42..08aa83c 100644
--- a/tests/test__auth.py
+++ b/tests/test__auth.py
@@ -12,13 +12,13 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import unittest
 import mock
 
 import google.auth.credentials
 import google_auth_httplib2
 import httplib2
 import oauth2client.client
-import unittest2 as unittest
 
 from googleapiclient import _auth
 
diff --git a/tests/test_channel.py b/tests/test_channel.py
index 8a46bf0..fe33731 100644
--- a/tests/test_channel.py
+++ b/tests/test_channel.py
@@ -3,8 +3,8 @@
 
 __author__ = "jcgregorio@google.com (Joe Gregorio)"
 
-import unittest2 as unittest
 import datetime
+import unittest
 
 from googleapiclient import channel
 from googleapiclient import errors
diff --git a/tests/test_discovery.py b/tests/test_discovery.py
index 2f3f028..9559bf6 100644
--- a/tests/test_discovery.py
+++ b/tests/test_discovery.py
@@ -35,7 +35,7 @@
 import pickle
 import re
 import sys
-import unittest2 as unittest
+import unittest
 import urllib
 
 from parameterized import parameterized
diff --git a/tests/test_discovery_cache.py b/tests/test_discovery_cache.py
index 2c3efd8..cd53318 100644
--- a/tests/test_discovery_cache.py
+++ b/tests/test_discovery_cache.py
@@ -18,7 +18,7 @@
 """Discovery document cache tests."""
 
 import datetime
-import unittest2 as unittest
+import unittest
 
 import mock
 
diff --git a/tests/test_errors.py b/tests/test_errors.py
index 955526f..7a2cfde 100644
--- a/tests/test_errors.py
+++ b/tests/test_errors.py
@@ -21,7 +21,7 @@
 __author__ = "afshar@google.com (Ali Afshar)"
 
 
-import unittest2 as unittest
+import unittest
 import httplib2
 
 
diff --git a/tests/test_http.py b/tests/test_http.py
index 5484269..852cd7e 100644
--- a/tests/test_http.py
+++ b/tests/test_http.py
@@ -31,7 +31,7 @@
 import logging
 import mock
 import os
-import unittest2 as unittest
+import unittest
 import urllib
 import random
 import socket
diff --git a/tests/test_json_model.py b/tests/test_json_model.py
index 416b7be..1ddc1c7 100644
--- a/tests/test_json_model.py
+++ b/tests/test_json_model.py
@@ -26,7 +26,7 @@
 import json
 import pkg_resources
 import platform
-import unittest2 as unittest
+import unittest
 import urllib
 
 import googleapiclient.model
diff --git a/tests/test_mocks.py b/tests/test_mocks.py
index d0a0ff0..287da95 100644
--- a/tests/test_mocks.py
+++ b/tests/test_mocks.py
@@ -24,7 +24,7 @@
 
 import httplib2
 import os
-import unittest2 as unittest
+import unittest
 
 from googleapiclient.errors import HttpError
 from googleapiclient.errors import UnexpectedBodyError
diff --git a/tests/test_model.py b/tests/test_model.py
index c3c936c..07d2261 100644
--- a/tests/test_model.py
+++ b/tests/test_model.py
@@ -23,7 +23,7 @@
 
 __author__ = "jcgregorio@google.com (Joe Gregorio)"
 
-import unittest2 as unittest
+import unittest
 
 from googleapiclient.model import BaseModel
 from googleapiclient.model import makepatch
diff --git a/tests/test_protobuf_model.py b/tests/test_protobuf_model.py
index 4479b13..68e3963 100644
--- a/tests/test_protobuf_model.py
+++ b/tests/test_protobuf_model.py
@@ -22,7 +22,7 @@
 
 __author__ = "mmcdonald@google.com (Matt McDonald)"
 
-import unittest2 as unittest
+import unittest
 import httplib2
 
 from googleapiclient.model import ProtocolBufferModel
diff --git a/tests/test_schema.py b/tests/test_schema.py
index f5fd518..b288908 100644
--- a/tests/test_schema.py
+++ b/tests/test_schema.py
@@ -19,7 +19,7 @@
 
 import json
 import os
-import unittest2 as unittest
+import unittest
 
 from googleapiclient.schema import Schemas