tests/test-extra-filelog-entry.t

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

Issue351: mq: qrefresh can create extra revlog entry

  $ echo "[extensions]" >> $HGRCPATH
  $ echo "mq=" >> $HGRCPATH

  $ hg init
  $ hg qinit

  $ echo b > b
  $ hg ci -A -m foo
  adding b

  $ echo cc > b
  $ hg qnew -f foo.diff
  $ echo b > b
  $ hg qrefresh

  $ hg debugindex b
     rev linkrev nodeid       p1           p2
       0       0 1e88685f5dde 000000000000 000000000000