Update pytest (#6768)

* Update pytest to 5.x

* Ensure test de-monkeypatches auth on failure

* Fix pytest.raises compat issue

Author: rpkilby

requirements/requirements-testing.txt

@@ -1,4 +1,4 @@
 # Pytest for running the tests.
-pytest>=4.5.0,<4.6
-pytest-django>=3.4.8,<3.5
+pytest>=5.0,<5.1
+pytest-django>=3.5.1,<3.6
 pytest-cov>=2.7.1

tests/authentication/test_authentication.py

@@ -533,11 +533,13 @@ class MockUser:
             is_active = False
         old_authenticate = authentication.authenticate
         authentication.authenticate = lambda **kwargs: MockUser()
-        auth = authentication.BasicAuthentication()
-        with pytest.raises(exceptions.AuthenticationFailed) as error:
-            auth.authenticate_credentials('foo', 'bar')
-        assert 'User inactive or deleted.' in str(error)
-        authentication.authenticate = old_authenticate
+        try:
+            auth = authentication.BasicAuthentication()
+            with pytest.raises(exceptions.AuthenticationFailed) as exc_info:
+                auth.authenticate_credentials('foo', 'bar')
+            assert 'User inactive or deleted.' in str(exc_info.value)
+        finally:
+            authentication.authenticate = old_authenticate
 
 
 @override_settings(ROOT_URLCONF=__name__,