https://bugzilla.wikimedia.org/show_bug.cgi?id=55225
--- Comment #1 from Kunal Mehta (Legoktm) legoktm.wikipedia@gmail.com --- I am also getting this bug from category.py in -r9851
$ python category.py move -from:"US Payment Processor" -to:"US Payment Processor project" -pt:0
Happens for some articles not others.