T120733 changes ContribsPager to use 'start' and 'end' parameters, rather than 'year' and 'month.' SpecialContributions was modified to convert the legacy 'year' and 'month' options to use the new 'start' and 'end' options, but ApiFeedContributions (the other class to use ContribsPager) was not modified, which breaks action=feedcontributions filtering by year/month.
[Fri Jun 2 08:40:12 2017] [hphp] [2178:7f9ee77ff700:88675:000001] [] \nNotice: Undefined index: start in /srv/mediawiki/tags/2017-06-01_14:16:17/includes/specials/pagers/ContribsPager.php on line 82 [Fri Jun 2 08:40:12 2017] [hphp] [2178:7f9ee77ff700:88675:000002] [] \nNotice: Undefined index: end in /srv/mediawiki/tags/2017-06-01_14:16:17/includes/specials/pagers/ContribsPager.php on line 85