Make all single-constraint TypeVars use bound= insteads (plus hack) (#1118)

Another attempt for #804, to unblock python/mypy#2626.
There's a work-around here for python/mypy#1551.

Author: gvanrossum

stdlib/2and3/plistlib.pyi

@@ -9,7 +9,7 @@ from enum import Enum
 import sys
 
 mm = MutableMapping[str, Any]
-_D = TypeVar('_D', mm)
+_D = TypeVar('_D', bound=mm)
 if sys.version_info >= (3,):
     _Path = str
 else:

stdlib/3/unittest/__init__.pyi

@@ -12,14 +12,15 @@ from contextlib import ContextManager
 
 
 _T = TypeVar('_T')
-_FT = TypeVar('_FT', Callable[[Any], Any])
+_FT = TypeVar('_FT', bound=Callable[[Any], Any])
 _E = TypeVar('_E', bound=Exception)
 
 
-def skip(reason: str) -> Callable[[_FT], _FT]: ...
-def skipIf(condition: object, reason: str) -> Callable[[_FT], _FT]: ...
-def skipUnless(condition: object, reason: str) -> Callable[[_FT], _FT]: ...
 def expectedFailure(func: _FT) -> _FT: ...
+# TODO: Once python/mypy#1551 is fixed, the following need _FT instead of Any
+def skip(reason: str) -> Callable[[Any], Any]: ...
+def skipIf(condition: object, reason: str) -> Callable[[Any], Any]: ...
+def skipUnless(condition: object, reason: str) -> Callable[[Any], Any]: ...
 
 class SkipTest(Exception):
     def __init__(self, reason: str) -> None: ...