tests/failfilemerge.py

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

# extension to emulate interrupting filemerge._filemerge

from __future__ import absolute_import

from mercurial import (
    error,
    extensions,
    filemerge,
)


def failfilemerge(
    filemergefn, premerge, repo, wctx, mynode, orig, fcd, fco, fca, labels=None
):
    raise error.Abort(b"^C")
    return filemergefn(premerge, repo, mynode, orig, fcd, fco, fca, labels)


def extsetup(ui):
    extensions.wrapfunction(filemerge, '_filemerge', failfilemerge)