[fix] do not call signature(obj) for non-callables. signature, will check and raise a exception where the message will contain obj.__repr__ and that can be very expensive on certain objects.

IPython/core/oinspect.py

@@ -416,6 +416,8 b' class Inspector(Colorable):'
 
         If any exception is generated, None is returned instead and the
         exception is suppressed."""
+        if not callable(obj):
+            return None        
         try:
             return _render_signature(signature(obj), oname)
         except: