Add py2 stubs for multiprocessing.Queue (#1829)

This is basically the same API as in Python 3.

stdlib/2/multiprocessing/__init__.pyi

@@ -1,11 +1,29 @@
+from typing import Optional, TypeVar
+
 from multiprocessing.process import Process as Process, current_process as current_process, active_children as active_children
 from multiprocessing.util import SUBDEBUG as SUBDEBUG, SUBWARNING as SUBWARNING
+from Queue import Queue as _BaseQueue
 
 class ProcessError(Exception): ...
 class BufferTooShort(ProcessError): ...
 class TimeoutError(ProcessError): ...
 class AuthenticationError(ProcessError): ...
 
+_T = TypeVar('_T')
+
+class Queue(_BaseQueue[_T]):
+    def __init__(self, maxsize: int = ...) -> None: ...
+    def get(self, block: bool = ..., timeout: Optional[float] = ...) -> _T: ...
+    def put(self, item: _T, block: bool = ..., timeout: Optional[float] = ...) -> None: ...
+    def qsize(self) -> int: ...
+    def empty(self) -> bool: ...
+    def full(self) -> bool: ...
+    def put_nowait(self, item: _T) -> None: ...
+    def get_nowait(self) -> _T: ...
+    def close(self) -> None: ...
+    def join_thread(self) -> None: ...
+    def cancel_join_thread(self) -> None: ...
+
 def Manager(): ...
 def Pipe(duplex=True): ...
 def cpu_count() -> int: ...
@@ -19,7 +37,6 @@ def Condition(lock=None): ...
 def Semaphore(value=1): ...
 def BoundedSemaphore(value=1): ...
 def Event(): ...
-def Queue(maxsize=0): ...
 def JoinableQueue(maxsize=0): ...
 def Pool(processes=None, initializer=None, initargs=..., maxtasksperchild=None): ...
 def RawValue(typecode_or_type, *args): ...