don't limit hypothesis's time to generate valid test permutations (#4525)

* don't limit hypothesis's time to generate valid test permutations

* add a comment

* lol
diff --git a/tests/hypothesis/test_fernet.py b/tests/hypothesis/test_fernet.py
index c652869..5f8f5f5 100644
--- a/tests/hypothesis/test_fernet.py
+++ b/tests/hypothesis/test_fernet.py
@@ -2,12 +2,17 @@
 # 2.0, and the BSD License. See the LICENSE file in the root of this repository
 # for complete details.
 
-from hypothesis import given
+from hypothesis import given, settings, unlimited
 from hypothesis.strategies import binary
 
 from cryptography.fernet import Fernet
 
 
+# Unlimited timeout will become the default in the future. When it does
+# we should remove this. See:
+# https://hypothesis.readthedocs.io/en/latest/settings.html
+# #hypothesis.settings.timeout
+@settings(deadline=None, timeout=unlimited)
 @given(binary())
 def test_fernet(data):
     f = Fernet(Fernet.generate_key())