bpo-41620: TestCase.run() now always return a TestResult instance (GH-28030)

Previously it returned None if the test class or method was
decorated with a skipping decorator.

Co-authored-by: Iman Tabrizian <iman.tabrizian@gmail.com>

Lib/unittest/case.py

@@ -575,7 +575,7 @@ def run(self, result=None):
                 skip_why = (getattr(self.__class__, '__unittest_skip_why__', '')
                             or getattr(testMethod, '__unittest_skip_why__', ''))
                 self._addSkip(result, self, skip_why)
-                return
+                return result
 
             expecting_failure = (
                 getattr(self, "__unittest_expecting_failure__", False) or