--- a/contrib/revsetbenchmarks.py	Wed Feb 10 09:06:08 2016 -0800
+++ b/contrib/revsetbenchmarks.py	Wed Feb 10 12:39:25 2016 -0800
@@ -63,7 +63,7 @@
         return parseoutput(output)
     except CalledProcessError as exc:
         print >> sys.stderr, 'abort: cannot run revset benchmark: %s' % exc.cmd
-        if exc.output is None:
+        if getattr(exc, 'output', None) is None: # no output before 2.7
             print >> sys.stderr, '(no output)'
         else:
             print >> sys.stderr, exc.output