use importlib.machinery when available

avoids deprecation warning on startup, and allows tests to pass with PYTHONWARNINGS=d

closes  #4051

candidate for backport to 1.2

IPython/core/completerlib.py

@@ -17,12 +17,19 b' from __future__ import print_function'
 
 # Stdlib imports
 import glob
-import imp
 import inspect
 import os
 import re
 import sys
 
+try:
+    # Python 3
+    from importlib.machinery import all_suffixes
+    _suffixes = all_suffixes()
+except ImportError:
+    from imp import get_suffixes
+    _suffixes = [ s[0] for s in get_suffixes() ]
+
 # Third-party imports
 from time import time
 from zipimport import zipimporter
@@ -51,7 +58,7 b' TIMEOUT_GIVEUP = 20'
 import_re = re.compile(r'(?P<name>[a-zA-Z_][a-zA-Z0-9_]*?)'
                        r'(?P<package>[/\\]__init__)?'
                        r'(?P<suffix>%s)$' %
-                       r'|'.join(re.escape(s[0]) for s in imp.get_suffixes()))
+                       r'|'.join(re.escape(s) for s in _suffixes))
 
 # RE for the ipython %run command (python + ipython scripts)
 magic_run_re = re.compile(r'.*(\.ipy|\.ipynb|\.py[w]?)$')