Fix edge case with tearDown() method

Author: mdmintz

seleniumbase/fixtures/base_case.py

@@ -2734,7 +2734,7 @@ def tearDown(self):
         """
         has_exception = False
         if sys.version.startswith('3') and hasattr(self, '_outcome'):
-            if self._outcome.errors:
+            if hasattr(self._outcome, 'errors') and self._outcome.errors:
                 has_exception = True
         else:
             has_exception = sys.exc_info()[1] is not None