Change numerous default values to ... (#1722)

This is the convention, and some default values (e.g. strings) apparently
break pytype.

third_party/2/dateutil/parser.pyi

@@ -27,13 +27,13 @@ class parserinfo(object):
     def validate(self, res: datetime) -> bool: ...
 
 class parser(object):
-    def __init__(self, info: Optional[parserinfo] = None) -> None: ...
+    def __init__(self, info: Optional[parserinfo] = ...) -> None: ...
     def parse(self, timestr: Union[str, unicode, IO[unicode]],
-              default: Optional[datetime] = None,
+              default: Optional[datetime] = ...,
               ignoretz: bool = ..., tzinfos: Optional[Dict[Union[str, unicode], tzinfo]] = None,
               **kwargs: Any) -> datetime: ...
 
 DEFAULTPARSER = ...  # type: parser
 def parse(timestr: Union[str, unicode, IO[unicode]],
-          parserinfo: Optional[parserinfo] = None,
+          parserinfo: Optional[parserinfo] = ...,
           **kwargs: Any) -> datetime: ...

third_party/2/google/protobuf/message_factory.pyi

@@ -6,7 +6,7 @@ from .descriptor_pool import DescriptorPool
 
 class MessageFactory:
     pool = ...  # type: Any
-    def __init__(self, pool: Optional[DescriptorPool] = None) -> None: ...
+    def __init__(self, pool: Optional[DescriptorPool] = ...) -> None: ...
     def GetPrototype(self, descriptor: Descriptor) -> Type[Message]: ...
     def GetMessages(self, files: Iterable[str]) -> Dict[str, Type[Message]]: ...
 

third_party/2/werkzeug/wrappers.pyi

@@ -82,8 +82,8 @@ class BaseResponse:
                  headers: Optional[Union[Headers,
                                          Mapping[basestring, basestring],
                                          Sequence[Tuple[basestring, basestring]]]] = None,
-                 mimetype: Optional[basestring] = None,
-                 content_type: Optional[basestring] = None,
+                 mimetype: Optional[basestring] = ...,
+                 content_type: Optional[basestring] = ...,
                  direct_passthrough: Optional[bool] = False) -> None: ...
     def call_on_close(self, func): ...
     @classmethod