[PATCH] py3: make check-py3-compat.py import importlib only if necessary

[Yuya Nishihara]

# HG changeset patch
# User Yuya Nishihara <yuya at tcha.org>
# Date 1476025354 -7200
#      Sun Oct 09 17:02:34 2016 +0200
# Node ID 7da151679301cf2a8331e411597f648bf3dce6b2
# Parent  8e42dfde93d10e099040e9b57c70b7774235d883
py3: make check-py3-compat.py import importlib only if necessary

importlib isn't available on Python 2.6, and it isn't necessary for Py2
checks.

diff --git a/contrib/check-py3-compat.py b/contrib/check-py3-compat.py
--- a/contrib/check-py3-compat.py
+++ b/contrib/check-py3-compat.py
@@ -10,7 +10,6 @@
 from __future__ import absolute_import, print_function
 
 import ast
-import importlib
 import os
 import sys
 import traceback
@@ -41,6 +40,7 @@ def check_compat_py2(f):
 
 def check_compat_py3(f):
     """Check Python 3 compatibility of a file with Python 3."""
+    import importlib  # not available on Python 2.6
     with open(f, 'rb') as fh:
         content = fh.read()