Make all third party mirrors sync from T1 mirrors
All third party mirrors must synchronize from our tier 1 (dl-N) mirrors, and not from master.
Therefore we must contact the admins for all third party mirrors and notify them of this.
A list of contacts are in the git.a.o:infra/mirrors repository.
(from redmine: issue id 8428, created on 2018-01-26)
- parent #8426