re2: feed unicode string to re2 module when necessary My previous test were using the `pyre2` Python project, that wrap the Google RE2 library in python as a `re2` module and accept bytes as input. However the `fb-re2` Python project is also offering a wrapping of the Google RE2 library in python as a `re2` module ans accept only unicode on python3. So we detect this situation and convert thing to unicode when necessary. Hooray… We should consider using a rust wrapping for regexp handling. We needs regexps in Rust anyway and this give use more control with less variants and more sanity. Differential Revision: https://phab.mercurial-scm.org/D10284