contint: pin python-voluptuous at 0.6.1-1~wmf1

0.6.1-4 is no more, it was mostly an experiment. The official Wikimedia
package is now 0.6.1-1~wmf1 uploaded by Faidon this tuesday.

Change-Id: Iab8578a2652eb0d9794bfad66ae2b4931dd2d44b
Merge "contint: pin python-voluptuous at 0.6.1-1~wmf1" into production