the following changes have been pushed to bugzilla.mozilla.org:
-  merge-users.pl fails if both users have bug_user_last_visit entries for the same bug
-  migrate mentors from the whiteboard to the mentor field
-  “No QA contact” represented by “” instead of null
-  Some empty fields are present as “” rather than being absent
-  updating a bug via an api or bulk bug update clears the mentor field
-  id, attachment.id, attachment.bug_id are returned as strings, not integers
discuss these changes on mozilla.tools.bmo.