Minor fixes to enable Python 3.5.2 support

Author: anselor

cmd2/utils.py

@@ -13,7 +13,7 @@
 import threading
 import unicodedata
 from enum import Enum
-from typing import Any, Callable, Dict, Iterable, List, Optional, TextIO, Type, Union
+from typing import Any, Callable, Dict, Iterable, List, Optional, TextIO, Union
 
 from . import constants
 
@@ -1041,15 +1041,20 @@ def categorize(func: Union[Callable, Iterable[Callable]], category: str) -> None
         setattr(func, constants.CMD_ATTR_HELP_CATEGORY, category)
 
 
-def get_defining_class(meth: Callable) -> Optional[Type]:
+def get_defining_class(meth):
     """
     Attempts to resolve the class that defined a method.
 
     Inspired by implementation published here:
         https://stackoverflow.com/a/25959545/1956611
 
+    TODO: Python 3.5.2 is unable to handle the type hints Callable and Optional[Type].
+          Restore proper type hints after we drop 3.5.2 support
+
     :param meth: method to inspect
+    :type meth: Callable
     :return: class type in which the supplied method was defined. None if it couldn't be resolved.
+    :rtype: Optional[Type]
     """
     if isinstance(meth, functools.partial):
         return get_defining_class(meth.func)