Handle missing six.viewkeys in trusty

This just pulls in the specific lines of code from six which are missing, so that we don't hit ImportErrors when trying to use mfdiff on trusty. bzr-revno: 19.1.1

1 files changed, 12 insertions, 1 deletions

diff --git a/mfdiff b/mfdiff
index 35313dc..66744a5 100755
--- a/mfdiff
+++ b/mfdiff
@@ -39,7 +39,18 @@ from optparse import OptionParser
 import apt
 import requests
 from debian.changelog import Changelog
-from six import iteritems, viewkeys
+from six import PY3, iteritems
+
+try:
+ from six import viewkeys
+except ImportError:
+ # The version of six in trusty doesn't have viewkeys, so pull in the six
+ # code from a more recent version if we can't get it directly from six.
+ import operator
+ if PY3:
+ viewkeys = operator.methodcaller("keys")
+ else:
+ viewkeys = operator.methodcaller("viewkeys")
 
 try:
 from apt import VersionCompare as version_compare