use try/except also for Py2.

imp.reload is actually aliased to the builtin

IPython/core/extensions.py

@@ -11,8 +11,7 b' import sys'
 from traitlets.config.configurable import Configurable
 from IPython.utils.path import ensure_dir_exists
 from traitlets import Instance
-from IPython.utils.py3compat import PY3
-if PY3:
+
     try: 
         from importlib import reload
     except ImportError :