Disallow the approval of submissions which would create variants of variants.
At this time the software doesn't let editors create submissions which would result in the creation of variants of variants. However, it's possible for a "to-be-made-into-parent" title to become a variant between the time the submission is created and the time it's approved. We need to add an extra check at the submission approval time. It should result in a red error message and the submission becoming unapprovable.
Anonymous
Implemented in common/viewers.py, installed in SVN 559 on 2020-11-11.