topic: drop compat.successorssets(), it's not used
The only place in topics that uses successorssets function is in evolvebits.py,
and it's using that function from obsutil directly.
# utility to setup pythonpath to point into the tested repository
export SRCDIR="`dirname $TESTDIR`"
if [ -n "$PYTHONPATH" ]; then
export HGTEST_ORIG_PYTHONPATH=$PYTHONPATH
if uname -o | grep -q Msys; then
export PYTHONPATH="$SRCDIR;$PYTHONPATH"
else
export PYTHONPATH=$SRCDIR:$PYTHONPATH
fi
else
export PYTHONPATH=$SRCDIR
fi