Automatically set severity when a bug has no severity and another bug with a severity is marked as its duplicate #1705
Description
See also #1574. Follow-up to #1672 (thanks to @calixteman for his idea in #1672 (comment)).
E.g. at this point https://bugzilla.mozilla.org/show_bug.cgi?id=1738056#a1662659_293943 we could have automatically set the severity from https://bugzilla.mozilla.org/show_bug.cgi?id=1735712, and avoided the needinfo later.
We could add this to the script that copies duplicate info, or to the script that suggests increasing severity based on duplicates.