Minor improvements and fix linting

src/_pytest/fixtures.py

@@ -895,7 +895,7 @@ def execute(self, request):
         if cached_result is not None:
             result, cache_key, err = cached_result
             # note: comparison with `==` can fail (or be expensive) for e.g.
-            # numpy arrays
+            # numpy arrays (#6497)
             if my_cache_key is cache_key:
                 if err is not None:
                     _, val, tb = err

testing/python/fixtures.py

@@ -1109,15 +1109,14 @@ def test_parameters_without_eq_semantics(self, scope, testdir):
             class NoEq1:  # fails on `a == b` statement
                 def __eq__(self, _):
                     raise RuntimeError
-            
+
             class NoEq2:  # fails on `if a == b:` statement
                 def __eq__(self, _):
                     class NoBool:
                         def __bool__(self):
                             raise RuntimeError
-                        __nonzero__ = __bool__  # for Py2
                     return NoBool()
-            
+
             import pytest
             @pytest.fixture(params=[NoEq1(), NoEq2()], scope={scope!r})
             def no_eq(request):
@@ -1128,7 +1127,9 @@ def test1(no_eq):
 
             def test2(no_eq):
                 pass
-        """.format(scope=scope)
+        """.format(
+                scope=scope
+            )
         )
         result = testdir.runpytest()
         result.stdout.fnmatch_lines(["*4 passed*"])