Allow Any return value for callbacks in retrbinary etc (#1567)

Fixes #1258

stdlib/2and3/ftplib.pyi

@@ -1,6 +1,6 @@
 # Stubs for ftplib (Python 2.7/3)
 import sys
-from typing import Optional, BinaryIO, Tuple, TextIO, Iterable, Callable, List, Union, Iterator, Dict, Text, TypeVar, Generic
+from typing import Optional, BinaryIO, Tuple, TextIO, Iterable, Callable, List, Union, Iterator, Dict, Text, TypeVar, Generic, Any
 from types import TracebackType
 from socket import socket
 from ssl import SSLContext
@@ -82,11 +82,11 @@ class FTP:
     # In practice, `rest` rest can actually be anything whose str() is an integer sequence, so to make it simple we allow integers.
     def ntransfercmd(self, cmd: Text, rest: Optional[_IntOrStr] = ...) -> Tuple[socket, int]: ...
     def transfercmd(self, cmd: Text, rest: Optional[_IntOrStr] = ...) -> socket: ...
-    def retrbinary(self, cmd: Text, callback: Callable[[bytes], None], blocksize: int = ..., rest: Optional[_IntOrStr] = ...) -> str: ...
-    def storbinary(self, cmd: Text, fp: BinaryIO, blocksize: int = ..., callback: Optional[Callable[[bytes], None]] = ..., rest: Optional[_IntOrStr] = ...) -> str: ...
+    def retrbinary(self, cmd: Text, callback: Callable[[bytes], Any], blocksize: int = ..., rest: Optional[_IntOrStr] = ...) -> str: ...
+    def storbinary(self, cmd: Text, fp: BinaryIO, blocksize: int = ..., callback: Optional[Callable[[bytes], Any]] = ..., rest: Optional[_IntOrStr] = ...) -> str: ...
 
-    def retrlines(self, cmd: Text, callback: Optional[Callable[[str], None]] = ...) -> str: ...
-    def storlines(self, cmd: Text, fp: BinaryIO, callback: Optional[Callable[[bytes], None]] = ...) -> str: ...
+    def retrlines(self, cmd: Text, callback: Optional[Callable[[str], Any]] = ...) -> str: ...
+    def storlines(self, cmd: Text, fp: BinaryIO, callback: Optional[Callable[[bytes], Any]] = ...) -> str: ...
 
     def acct(self, password: Text) -> str: ...
     def nlst(self, *args: Text) -> List[str]: ...