reciprocity/ggrc-core — pull request #535 by SilasX (2013-11-08 20:02:39+00:00)
Title: Made assignee required, so blanks are rejected.

Per story [60365008](https://www.pivotaltracker.com/story/show/60365008). Getting server error if assignee fields are blank. Current spec is that assignee field is required so it should never get to this point; changing import process so that upload is rejected if these fields are blank.