[Merge] lp:~abompard/mailman/pgsql_upgrade into lp:mailman

[Aurélien Bompard]

OK I'll try to write some tests for this migration.
There's a workaround for #1170063 in the ticket that works for me, event if it's not perfect.
And with the SQLite lockups I reported long ago (#1091586), we can't afford to have neither SQLite nor PostgreSQL support...
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https://code.launchpad.net/~abompard/mailman/pgsql_upgrade/+merge/227289
Your team Mailman Coders is requested to review the proposed merge of lp:~abompard/mailman/pgsql_upgrade into lp:mailman.