Comment 0 for bug 1740543

While we have been strongly recommending Python 2.7 for some time, it has not been listed as a requirement. Mailman 2.1.22 introduced a call to re.sub() with a flags= argument that requires Python 2.7. The code in question will only be executed when archiving a message with no Date: header containing a valid date and no X-List-Received-At: header containing a valid date which will almost certainly only occur when bin/arch is processing a mbox containing such a message, so this is of minor importance, but is easily fixed so I'll fix it.