Add missing Dict imports.

stdlib/2/os/__init__.pyi

@@ -2,7 +2,7 @@
 
 from typing import (
     List, Tuple, Union, Sequence, Mapping, IO, Any, Optional, AnyStr, Iterator,
-    MutableMapping, NamedTuple, overload
+    Dict, MutableMapping, NamedTuple, overload
 )
 from . import path
 

stdlib/2/unittest.pyi

@@ -5,7 +5,7 @@
 # Only a subset of functionality is included.
 
 from typing import (
-    Any, Callable, Iterable, Tuple, List, TextIO, Sequence,
+    Any, Callable, Dict, Iterable, Tuple, List, TextIO, Sequence,
     overload, TypeVar, Pattern
 )
 from abc import abstractmethod, ABCMeta