discovery: move all setup into a 'modsetup' function
The various wrappings are moved into a function that live in the module and the
function is now properly called during 'uisetup'.
#require test-repo pyflakes
Copied from Mercurial core (60ee2593a270)
$ cd "`dirname "$TESTDIR"`"
run pyflakes on all tracked files ending in .py or without a file ending
(skipping binary file random-seed)
$ hg locate 'set:**.py or grep("^!#.*python")' 2>/dev/null \
> | xargs pyflakes 2>/dev/null