Fix errors in stubs when running in strict mode (#515)

stdlib/3/tempfile.pyi

@@ -3,7 +3,8 @@
 
 # based on http://docs.python.org/3.3/library/tempfile.html
 
-from typing import Tuple, BinaryIO
+from types import TracebackType
+from typing import BinaryIO, Optional, Tuple, Type
 
 # global variables
 tempdir = ...  # type: str
@@ -20,7 +21,7 @@ def TemporaryFile(
 def NamedTemporaryFile(
             mode: str = ..., buffering: int = ..., encoding: str = ...,
             newline: str = ..., suffix: str = ..., prefix: str = ...,
-            dir: str = ..., delete=...) -> BinaryIO:
+            dir: str = ..., delete: bool =...) -> BinaryIO:
     ...
 def SpooledTemporaryFile(
             max_size: int = ..., mode: str = ..., buffering: int = ...,
@@ -34,7 +35,9 @@ class TemporaryDirectory:
                  dir: str = ...) -> None: ...
     def cleanup(self) -> None: ...
     def __enter__(self) -> str: ...
-    def __exit__(self, type, value, traceback) -> bool: ...
+    def __exit__(self, exc_type: Optional[Type[BaseException]],
+                 exc_val: Optional[Exception],
+                 exc_tb: Optional[TracebackType]) -> bool: ...
 
 def mkstemp(suffix: str = ..., prefix: str = ..., dir: str = ...,
             text: bool = ...) -> Tuple[int, str]: ...

stdlib/3/unittest.pyi

@@ -8,6 +8,7 @@ from typing import (
 import logging
 import sys
 from types import ModuleType, TracebackType
+from contextlib import ContextManager
 
 
 _T = TypeVar('_T')
@@ -37,7 +38,7 @@ class TestCase:
     def run(self, result: Optional[TestResult] = ...) -> TestCase: ...
     def skipTest(self, reason: Any) -> None: ...
     if sys.version_info >= (3, 4):
-        def subTest(self, msg: Any = ..., **params: Any) -> None: ...
+        def subTest(self, msg: Any = ..., **params: Any) -> ContextManager[None]: ...
     def debug(self) -> None: ...
     def assertEqual(self, first: Any, second: Any, msg: Any = ...) -> None: ...
     def assertNotEqual(self, first: Any, second: Any,