"ERROR: The Gitlab server has rejected the proposed username, as it ends in the same suffix as a file extension that is registered to a MIME type in the Ruby ru

"ERROR: The Gitlab server has rejected the proposed username, as it ends in the same suffix as a file extension that is registered to a MIME type in the Ruby runtime under which the server runs. This list is quite long, and possibly difficult to retrieve, so we will not list it here, but you can find a list of extensions commonly used if you Google for MIME. Alternatively, if this makes no sense at all, ask a local alpha geek and they should be able to help. We understand this is weird, but the reasons for doing so are currently embargoed as they potentially have wide ranging security or stability consequences for a large number of installs. If you wouldn't mind, please do us a small one and keep quiet while we have a chance to prepare and distribute a patch without forcing anyone to forego any nights of sleep 18 months into a global pandemic complete with associated societal fracturing and potential economic collapse. Thank you for your cooperation on this easy, basic and very important matter." fixed it!