pushexperiment: remove use of obsolete._enabled pushexperiment.py was using obsolete._enabled but it didn't cause any tests to fail so I didn't see it. Let's go ahead and replace it with the new obsolete.isenabled() api.

syntax: re
/figures/[^/]+\.png$
^docs/build/
^docs/html/
^html/
\.pyc$
~$
\.swp$
\.orig$
\.rej$
\.err$
^tests/easy_run.sh$
^build/
^MANIFEST$
^docs/tutorials/.*\.rst$
\.ico$