Fix PathType for python < 3.6

Author: pkch

mypy/util.py

@@ -145,7 +145,8 @@ def id(self, o: object) -> int:
 if sys.version_info >= (3, 6):
     PathType = Union[AnyStr, 'os.PathLike[AnyStr]']
 else:
-    PathType = AnyStr
+    # Workaround; PathType = AnyStr would fail below when we use PathType[AnyStr]
+    PathType = Union[AnyStr]
 
 
 def _replace(src: PathType[AnyStr], dest: PathType[AnyStr], timeout: float = 1) -> None: