Pass str to on_rm_rf_error on py35

Author: nicoddemus

testing/test_tmpdir.py

@@ -387,17 +387,17 @@ def test_on_rm_rf_error(self, tmp_path):
         # unknown exception
         with pytest.warns(pytest.PytestWarning):
             exc_info = (None, RuntimeError(), None)
-            on_rm_rf_error(os.unlink, fn, exc_info, start_path=tmp_path)
+            on_rm_rf_error(os.unlink, str(fn), exc_info, start_path=tmp_path)
             assert fn.is_file()
 
         # unknown function
         with pytest.warns(pytest.PytestWarning):
             exc_info = (None, PermissionError(), None)
-            on_rm_rf_error(None, fn, exc_info, start_path=tmp_path)
+            on_rm_rf_error(None, str(fn), exc_info, start_path=tmp_path)
             assert fn.is_file()
 
         exc_info = (None, PermissionError(), None)
-        on_rm_rf_error(os.unlink, fn, exc_info, start_path=tmp_path)
+        on_rm_rf_error(os.unlink, str(fn), exc_info, start_path=tmp_path)
         assert not fn.is_file()