👌 Address code review

Edited the changelog for extra clarity, and to fire off auto-formatting

Oddly enough, keeping `filename='{filename!r}'` caused an error while
collecting tests, but getting rid of the single ticks fixed it
Hopefully closes #3191

changelog/3191.feature.rst

@@ -3,9 +3,14 @@ A warning is now issued when assertions are made directly against ``None``.
 This is a common source of confusion among new users, which write::
 
     assert mocked_object.assert_called_with(3, 4, 5, key='value')
-    
-When they should write::     
+
+When they should write::
 
     mocked_object.assert_called_with(3, 4, 5, key='value')
 
 Because the ``assert_called_with`` method of mock objects already executes an assertion.
+
+This warning will not be issued when ``None`` is explicitly checked
+    assert none_returning_fun() is None
+
+will not issue the warning

src/_pytest/assertion/rewrite.py

@@ -901,7 +901,7 @@ from warnings import warn_explicit
 warn_explicit(
     PytestWarning('assertion the value None, Please use "assert is None"'),
     category=None,
-    filename='{filename}',
+    filename={filename!r},
     lineno={lineno},
 )
             """.format(

testing/test_warnings.py

@@ -623,6 +623,8 @@ def test_removed_in_pytest4_warning_as_error(testdir, change_default):
     else:
         assert change_default in ("ini", "cmdline")
         result.stdout.fnmatch_lines(["* 1 passed in *"])
+
+
 class TestAssertionWarnings:
     @staticmethod
     def assert_result_warns(result):
@@ -660,7 +662,6 @@ class TestAssertionWarnings:
         result = testdir.runpytest()
         self.assert_result_warns(result)
 
-    @pytest.mark.xfail(strict=True)
     def test_assert_is_none_no_warn(self, testdir):
         """Tests a more simple case of `test_none_function_warns` where `assert None` is explicitly called"""
         testdir.makepyfile(
@@ -673,10 +674,9 @@ class TestAssertionWarnings:
             """
         )
         result = testdir.runpytest()
-        self.assert_result_warns(result)
+        result.stdout.fnmatch_lines(["*1 passed in*"])
 
-    @pytest.mark.xfail(strict=True)
     def test_false_function_no_warn(self, testdir):
         self.create_file(testdir, False)
         result = testdir.runpytest()
-        self.assert_result_warns(result)
+        result.stdout.fnmatch_lines(["*1 failed in*"])