We need to test all the front ends with Python 3 and get them working
with it (front ends are both not well-covered by the testsuite, and a
place where bytes/string conversions are particularly likely to be
needed).  By front ends I mean the different web interfaces where
doc/installation.txt says "There are five web interfaces to choose from"
(and then lists six, not five), not just what's in the frontends
directory - all six need to be made to work with Python 3 for us to be
able to document Python 3 support as on a par with that for Python 3.