Handle org where 'all' team doesn't have access to 'people' repo

[rtyley]

If the 'all' team doesn't have access to the 'people' repo, members of the org (who don't have read access to the 'people' repo) can not be assigned to issues in that repo - and so gu-who crashes.

We should probably automatically make the 'all' team have access to the people repo, or at least let the user know it's a problem.