Add DeprecationWarning for path_mtime

Co-authored-by: rashansmith <[email protected]>

Author: tomasr8

Lib/importlib/abc.py

@@ -199,6 +199,11 @@ class SourceLoader(_bootstrap_external.SourceLoader, ResourceLoader, ExecutionLo
 
     def path_mtime(self, path):
         """Return the (int) modification time for the path (str)."""
+        import warnings
+        warnings.warn("SourceLoader.path_mtime is deprecated in favour of "
+                      "SourceLoader.path_stats().",
+                      DeprecationWarning,
+                      stacklevel=2)
         if self.path_stats.__func__ is SourceLoader.path_stats:
             raise OSError
         return int(self.path_stats(path)['mtime'])

Lib/test/test_importlib/test_abc.py

@@ -913,5 +913,25 @@ def test_universal_newlines(self):
                          SourceOnlyLoaderMock=SPLIT_SOL)
 
 
+class SourceLoaderDeprecationWarningsTests(unittest.TestCase):
+    """Tests SourceLoader deprecation warnings."""
+
+    def test_deprecated_path_mtime(self):
+        from importlib.abc import SourceLoader
+        class DummySourceLoader(SourceLoader):
+            def get_data(self, path):
+                return b''
+
+            def get_filename(self, fullname):
+                return 'foo.py'
+
+            def path_stats(self, path):
+                return {'mtime': 1}
+
+        loader = DummySourceLoader()
+        with self.assertWarns(DeprecationWarning):
+            loader.path_mtime('foo.py')
+
+
 if __name__ == '__main__':
     unittest.main()