[Merge] lp:~abompard/mailman/bug-1158721 into lp:mailman

Aurélien Bompard has proposed merging lp:~abompard/mailman/bug-1158721 into lp:mailman. Requested reviews: Mailman Coders (mailman-coders) Related bugs: Bug #1158721 in GNU Mailman: "Emails without a text/plain part crash the Approved rule" https://bugs.launchpad.net/mailman/+bug/1158721 For more details, see: https://code.launchpad.net/~abompard/mailman/bug-1158721/+merge/243229 Emails without a text/plain part crash the Approved rule, this branch contains the fix for bug #1158721. -- Your team Mailman Coders is requested to review the proposed merge of lp:~abompard/mailman/bug-1158721 into lp:mailman.