Backport PR #5818: interpret any exception in getcallargs as not callable

some object (mock) lie to callable

closes  #5817

IPython/core/formatters.py

@@ -76,7 +76,7 b' def _valid_formatter(f):'
         # anything that works with zero args should be okay
         try:
             inspect.getcallargs(f)
-        except TypeError:
+        except Exception:
             return False
         else:
             return True