Backport #19217
If a mirror fails to be synchronised it should be pushed to the bottom of the queue
of the awaiting mirrors to be synchronised. At present if there LIMIT number of
broken mirrors they can effectively prevent all other mirrors from being synchronized
as their last_updated time will remain earlier than other mirrors.
Signed-off-by: Andrew Thornton <art27@cantab.net>
* Some refactors related repository model
* Move more methods out of repository
* Move repository into models/repo
* Fix test
* Fix test
* some improvements
* Remove unnecessary function