Catch urllib's HTTPException and give a meaningful error message to the user. Usually urllib only throws HTTPError exceptions, which already are a subclass of IOError.

#!/bin/sh

hg
hg -q
hg help
hg -q help
hg add -h
hg add --skjdfks
hg help diff
hg help status
hg -q help status
hg help foo
hg skjdfks

exit 0