Merge pull request #5818 from minrk/catch-getcallargs

interpret any exception in getcallargs as not callable

IPython/core/formatters.py

@@ -74,7 +74,7 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