check_compat.py was adapted from gps' check-py3-compat.py in mercurial:
https://www.mercurial-scm.org/repo/hg/file/tip/contrib/check-py3-compat.py
The py3 linter simply runs ast.parse(f) for each file being linted. Any syntax errors
are formatted as mozlint results and dumped to stdout as json. I looked into also
importing the file (using 3.5+'s importlib.util.spec_from_file_location), but there
were too many problems:
1. Lots of false positives (e.g module not found)
2. Some files seemed to run indefinitely on import
I decided to punt on importing for now, we can always investigate in a follow-up.
The py2 linter runs ast.parse(f), and also checks that the file has:
from __future__ import absolute_import, print_function
Initially every python file in the tree is excluded from the py2 check, though
at least this makes it easy to find+fix, and new files in un-excluded
directories will automatically be linted.
MozReview-Commit-ID: ABtq9dnPo9T
