Cannot rename project

Summary

Cannot rename project clambin/ourorobos-fork to clambin/ouroborus: when I try I get an error "The form contains the following error: Name has already been taken"

There was previously a project 'clambin/ouroboros but I've had it deleted (and it no longer appears in my list of projects).

Steps to reproduce

• Open project clambin/ouroboros-fork
• Go to Settings / General
• Change project name to 'ouroboros' and save
• Error is shown

Example Project

https://gitlab.com/clambin/ouroboros-fork

What is the current bug behavior?

Gitlab reports the name is taken, but there's no such project anymore.

What is the expected correct behavior?

Rename the project to the new name.

Relevant logs and/or screenshots

The form contains the following error: Name has already been taken

Output of checks

This bug happens on GitLab.com

Results of GitLab environment info

Expand for output related to GitLab environment info

(For installations with omnibus-gitlab package run and paste the output of:
`sudo gitlab-rake gitlab:env:info`)

(For installations from source run and paste the output of:
`sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production`)

Results of GitLab application Check

Expand for output related to the GitLab application check

(For installations with omnibus-gitlab package run and paste the output of:
sudo gitlab-rake gitlab:check SANITIZE=true)
(For installations from source run and paste the output of:
sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true)
(we will only investigate if the tests are passing)

Possible fixes

N/A