Merge lp://staging/~jtv/launchpad/bug-409686 into lp://staging/launchpad

Notify owners of unpushed translations branches.

= Bug 409686 =

The Code UI unfortunately allows users to "register" a branch without populating it. From the Launchpad database's point of view, this is a perfectly good branch. From bzr's point of view, it just doesn't exist. With our daily translations exports to bzr branches, this situation has been showing up in logs as NotBranchError exceptions. I've been notifying these people of the problem by hand, but I got tired of it and the LOSA team got sick of looking at the log output on error-reports.

Here's a fix that catches this condition, logs it separately from "real" errors, and notifies the branch owner by email. (The branch owner is normally also the project owner; where they're not the same, it's the branch owner who should perform the necessary bzr steps). The branch owner will be receiving this every day, hopefully pushing towards a rapid resolution.

We won't be able to Q/A this on staging, beyond ensuring that the script doesn't break altogether. On production, we can pick a translatable project and temporarily enable translations exports to a branch we registered ourselves (but did not push to the server). Of course we'll also want to make sure that the regular exports still work as well.

To test:
{{{
./bin/test -vv -t 'translations.*to.branch'
}}}

No lint.

Jeroen