Add pathlib.Path.__enter__ and __exit__ (#2048)

stdlib/3.4/pathlib.pyi

@@ -1,6 +1,7 @@
 # Stubs for pathlib (Python 3.4)
 
 from typing import Any, Generator, IO, Optional, Sequence, Tuple, Type, TypeVar, Union, List
+from types import TracebackType
 import os
 import sys
 
@@ -52,6 +53,10 @@ class PurePosixPath(PurePath): ...
 class PureWindowsPath(PurePath): ...
 
 class Path(PurePath):
+    def __enter__(self) -> Path: ...
+    def __exit__(self, exc_type: Optional[Type[BaseException]],
+                 exc_value: Optional[BaseException],
+                 traceback: Optional[TracebackType]) -> Optional[bool]: ...
     @classmethod
     def cwd(cls: Type[_P]) -> _P: ...
     def stat(self) -> os.stat_result: ...