debian: replace build line with a override_dh_auto_build line
This is more in line with how dh is supposed to work. In particular,
dh_auto_build is functionally equivalent to the repeated "dh build
--with python2 --buildsystem=python_distutils" used currently.
syntax: re
/figures/[^/]+\.png$
^docs/build/
^docs/html/
^html/
\.pyc$
~$
\.swp$
\.orig$
\.rej$
\.err$
^tests/easy_run.sh$
^build/
^MANIFEST$
^docs/tutorials/.*\.rst$
\.ico$