tests/test-execute-bit.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

#require execbit

  $ hg init
  $ echo a > a
  $ hg ci -Am'not executable'
  adding a

  $ chmod +x a
  $ hg ci -m'executable'
  $ hg id
  79abf14474dc tip

Make sure we notice the change of mode if the cached size == -1:

  $ hg rm a
  $ hg revert -r 0 a
  $ hg debugstate
  n   0         -1 unset               a
  $ hg status
  M a

  $ hg up 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg id
  d69afc33ff8a
  $ test -x a && echo executable -- bad || echo not executable -- good
  not executable -- good