apply black and isort (#4287)

* apply black and isort

* move some type ignores

stdlib/2and3/genericpath.pyi

@@ -1,15 +1,19 @@
-from typing import Sequence, AnyStr, Text, Union
 import sys
+from typing import AnyStr, Sequence, Text, Union
 
 if sys.version_info >= (3, 0):
     def commonprefix(m: Sequence[str]) -> str: ...
+
 else:
     def commonprefix(m: Sequence[AnyStr]) -> AnyStr: ...
+
 if sys.version_info >= (3, 6):
     from builtins import _PathLike
     def exists(path: Union[AnyStr, _PathLike[AnyStr]]) -> bool: ...
+
 else:
     def exists(path: Text) -> bool: ...
+
 def isfile(path: Text) -> bool: ...
 def isdir(s: Text) -> bool: ...
 def getsize(filename: Text) -> int: ...
@@ -17,7 +21,6 @@ def getmtime(filename: Text) -> float: ...
 def getatime(filename: Text) -> float: ...
 def getctime(filename: Text) -> float: ...
 
-
 if sys.version_info >= (3, 4):
     def samestat(s1: str, s2: str) -> int: ...
     def samefile(f1: str, f2: str) -> int: ...