sanger/sequencescape — pull request #610 by mattdenner (2012-09-07 10:40:44+00:00)
Title: [#35525863] Repair migrations so that they are more rigorous

For some reason the migrations before this change were not correctly
setting the target_purpose_id information on request types. These
changes effectively define RequestType inside migrations and ensure that
RequestType#find_by_key return result is checked for nil.