Summary:
Make it possible to run edenscm via a "python package".
This makes it possible to run monkeytype [1] via debugpyhon:
./hg3 debugpython -- -m monkeytype run edenscm help log --pager=off
[1]: https://github.com/Instagram/MonkeyType
Reviewed By: farnz
Differential Revision: D19655850
fbshipit-source-id: 358f9dcf976141f798af2d57fb6392f2bca6a396