setup.py: remove unused and harmful code importing mercurial
This was failing on some build system we have. The import seemed to
succeed, but then mercurial.__all__ would fail. I don't know why, but
since it's unused anyway, let's just drop it.
syntax: re
/figures/[^/]+\.png$
^html/
\.pyc$
~$
\.swp$
\.orig$
\.rej$
\.err$
^tests/easy_run.sh$
^build/
^MANIFEST$
^docs/tutorials/.*\.rst$
\.ico$
tests/\.testtimes