[Dev] Some assignments from the PR bot fail due to anti-spam protection

[assignUser]

Describe the bug, including details regarding any error messages, version, and platform.

If a user has not commented on an issue and does not have write access to the repository it is not possible to assign them. This is a GitHub spam protection that can not be circumvented. We should check for successful assignment in the PR bot and otherwise add a comment with instruction on how to self-assign the ticket.

Component(s)

Developer Tools