DeprecationWarnings emitted from re.compile

[mattip]

Running python3.6 -mpytest tests raises a DeprecationWarning

tests/test_c_lexer.py:166
  /tmp/pycparser/tests/test_c_lexer.py:166: DeprecationWarning: invalid escape sequence \9
    '"jx\9"',

tests/test_c_lexer.py:169
  /tmp/pycparser/tests/test_c_lexer.py:169: DeprecationWarning: invalid escape sequence \9
    '"fo\9999999"',

-- Docs: https://docs.pytest.org/en/latest/warnings.html

It seems all the re.compile expressions should be using r raw strings?

xref numpy/numpy#14554

[eliben]

Thanks for the report. I'll accept PRs to fix this

[eliben]

I'm starting to plan for releasing a new version -- see #365

If you want this fix in, hurry up :-) I actually can't reproduce the warning, perhaps because I'm not using pytest.