If repository mirroring fails, keep trying the other mirrors
Summary: Ref T4338. Currently, if you have several mirrors and the first one fails, we won't try the other mirrors (since we'll throw and that will take us out of the mirroring process). Instead, try each mirror even if one fails, and then throw an AggregateException with all the failures.
Test Plan:
- Ran bin/repository mirror normally.
- Faked an exception, ran again, got the AggregateException I expected.
Reviewers: btrahan
Reviewed By: btrahan
CC: aran
Maniphest Tasks: T4338
Differential Revision: https://secure.phabricator.com/D8067