Switch usages of mypy_extensions.NoReturn over to typing.NoReturn. (#1942)

* Change mypy_extensions.NoReturn to typing.NoReturn everywhere.

stdlib/2/__builtin__.pyi

@@ -4,14 +4,13 @@
 # Python 3, and stub files conform to Python 3 syntax.
 
 from typing import (
-    TypeVar, Iterator, Iterable, overload,
+    TypeVar, Iterator, Iterable, NoReturn, overload,
     Sequence, Mapping, Tuple, List, Any, Dict, Callable, Generic, Set,
     AbstractSet, FrozenSet, Sized, Reversible, SupportsInt, SupportsFloat, SupportsAbs,
     SupportsRound, IO, BinaryIO, Union, AnyStr, MutableSequence, MutableMapping,
     MutableSet, ItemsView, KeysView, ValuesView, Optional, Container, Type
 )
 from abc import abstractmethod, ABCMeta
-from mypy_extensions import NoReturn
 
 _T = TypeVar('_T')
 _T_co = TypeVar('_T_co', covariant=True)

stdlib/2/dummy_thread.pyi

@@ -1,5 +1,4 @@
-from mypy_extensions import NoReturn
-from typing import Any, Callable, Dict, Optional, Tuple
+from typing import Any, Callable, Dict, NoReturn, Optional, Tuple
 
 class error(Exception):
     def __init__(self, *args: Any) -> None: ...

stdlib/2/os/__init__.pyi

@@ -7,10 +7,9 @@ from posix import stat_result as stat_result  # TODO: use this, see https://gith
 import sys
 from typing import (
     Mapping, MutableMapping, Dict, List, Any, Tuple, Iterator, overload, Union, AnyStr,
-    Optional, Generic, Set, Callable, Text, Sequence, IO, NamedTuple, TypeVar
+    Optional, Generic, Set, Callable, Text, Sequence, IO, NamedTuple, NoReturn, TypeVar
 )
 from . import path as path
-from mypy_extensions import NoReturn
 
 _T = TypeVar('_T')
 

stdlib/2/pydoc.pyi

@@ -1,5 +1,4 @@
-from typing import Any, AnyStr, Callable, Container, Dict, IO, List, Mapping, MutableMapping, Optional, Tuple, Type, Union
-from mypy_extensions import NoReturn
+from typing import Any, AnyStr, Callable, Container, Dict, IO, List, Mapping, MutableMapping, NoReturn, Optional, Tuple, Type, Union
 from repr import Repr
 
 from types import FunctionType, MethodType, ModuleType, TracebackType

stdlib/2/sys.pyi

@@ -1,11 +1,10 @@
 """Stubs for the 'sys' module."""
 
 from typing import (
-    IO, Union, List, Sequence, Any, Dict, Tuple, BinaryIO, Optional, Callable,
-    overload, Text, Type,
+    IO, NoReturn, Union, List, Sequence, Any, Dict, Tuple, BinaryIO, Optional,
+    Callable, overload, Text, Type,
 )
 from types import FrameType, ModuleType, TracebackType, ClassType
-from mypy_extensions import NoReturn
 
 class _flags:
     bytes_warning = ...  # type: int

stdlib/2/unittest.pyi

@@ -2,10 +2,9 @@
 
 # Based on http://docs.python.org/2.7/library/unittest.html
 
-from mypy_extensions import NoReturn
 from typing import (Any, Callable, Dict, FrozenSet, Iterable, Iterator,
-                    List, Optional, overload, Pattern, Sequence, Set, Text,
-                    TextIO, Tuple, Type, TypeVar, Union)
+                    List, NoReturn, Optional, overload, Pattern, Sequence, Set,
+                    Text, TextIO, Tuple, Type, TypeVar, Union)
 from abc import abstractmethod, ABCMeta
 import types