Change callability check

TypeErrors are thrown in a wide variety of situations, most of which
have nothing to do with calling an uncallable object. The appropriate
test is to use the built-in callable() function, which actually
tests if the object is callable.

evennia/commands/cmdset.py

@@ -296,9 +296,9 @@ class CmdSet(with_metaclass(_CmdSetMeta, object)):
             result (any): An instantiated Command or the input unmodified.
 
         """
-        try:
+        if callable(cmd):
             return cmd()
-        except TypeError:
+        else:
             return cmd
 
     def _duplicate(self):