Add flags to pass on --warn-unused-ignores and --no-implicit-optional to mypy (#1421)

* Add flags to pass on --warn-unused-ignores and --no-implicit-optional to mypy
* Make implicit Optional explicit in arg types (2and3 part)
* Convert {stdlib,third_party}/2 to explicit Optional

stdlib/2and3/asynchat.pyi

@@ -2,7 +2,7 @@ from abc import abstractmethod
 import asyncore
 import socket
 import sys
-from typing import Union, Tuple, Sequence
+from typing import Optional, Sequence, Tuple, Union
 
 
 class simple_producer:
@@ -12,7 +12,7 @@ class simple_producer:
 class async_chat(asyncore.dispatcher):
     ac_in_buffer_size = ...  # type: int
     ac_out_buffer_size = ...  # type: int
-    def __init__(self, sock: socket.socket = None, map: asyncore._maptype = None) -> None: ...
+    def __init__(self, sock: Optional[socket.socket] = None, map: Optional[asyncore._maptype] = None) -> None: ...
 
     @abstractmethod
     def collect_incoming_data(self, data: bytes) -> None: ...

stdlib/2and3/asyncore.pyi

@@ -25,7 +25,7 @@ def poll2(timeout: float = ..., map: _maptype = ...) -> None: ...
 
 poll3 = poll2
 
-def loop(timeout: float = ..., use_poll: bool = ..., map: _maptype = ..., count: int = None) -> None: ...
+def loop(timeout: float = ..., use_poll: bool = ..., map: _maptype = ..., count: Optional[int] = None) -> None: ...
 
 
 # Not really subclass of socket.socket; it's only delegation.
@@ -39,7 +39,7 @@ class dispatcher:
     closing = ...  # type: bool
     ignore_log_types = ...  # type: frozenset[str]
 
-    def __init__(self, sock: socket.socket = None, map: _maptype = ...) -> None: ...
+    def __init__(self, sock: Optional[socket.socket] = None, map: _maptype = ...) -> None: ...
     def add_channel(self, map: _maptype = ...) -> None: ...
     def del_channel(self, map: _maptype = ...) -> None: ...
     def create_socket(self, family: int, type: int) -> None: ...

stdlib/2and3/bz2.pyi

@@ -1,21 +1,21 @@
 # Stubs for bz2
 
-from typing import Any, BinaryIO, TextIO, IO, Union
+from typing import Any, BinaryIO, TextIO, IO, Optional, Union
 
 def compress(data: bytes, compresslevel: int = ...) -> bytes: ...
 def decompress(data: bytes) -> bytes: ...
 
 def open(filename: Union[str, bytes, IO[Any]],
          mode: str = 'rb',
-         encoding: str = None,
-         errors: str = None,
-         newline: str = None) -> IO[Any]: ...
+         encoding: Optional[str] = None,
+         errors: Optional[str] = None,
+         newline: Optional[str] = None) -> IO[Any]: ...
 
 class BZ2File(BinaryIO):
     def __init__(self,
                  filename: Union[str, bytes, IO[Any]],
                  mode: str = "r",
-                 buffering: Any = None,
+                 buffering: Optional[Any] = None,
                  compresslevel: int = 9) -> None: ...
 
 class BZ2Compressor(object):

stdlib/2and3/pdb.pyi

@@ -1,15 +1,15 @@
 # NOTE: This stub is incomplete - only contains some global functions
 
-from typing import Any, Dict
+from typing import Any, Dict, Optional
 
 def run(statement: str,
-        globals: Dict[str, Any] = None,
-        locals: Dict[str, Any] = None) -> None:
+        globals: Optional[Dict[str, Any]] = None,
+        locals: Optional[Dict[str, Any]] = None) -> None:
     ...
 
 def runeval(expression: str,
-            globals: Dict[str, Any] = None,
-            locals: Dict[str, Any] = None) -> Any:
+            globals: Optional[Dict[str, Any]] = None,
+            locals: Optional[Dict[str, Any]] = None) -> Any:
     ...
 
 def runctx(statement: str,
@@ -23,7 +23,7 @@ def runcall(*args: Any, **kwds: Any) -> Any:
 def set_trace() -> None:
     ...
 
-def post_mortem(t: Any = None) -> None:
+def post_mortem(t: Optional[Any] = None) -> None:
     ...
 
 def pm() -> None: