D7544: subrepo: use pycompat.open directly instead of importing open from pycompat

[spectral (Kyle Lippincott)]

spectral added a comment.


  In D7544#110954 <https://phab.mercurial-scm.org/D7544#110954>, @mharbison72 wrote:
  
  > I don't think this is correct, because `open` is imported from `pycompat` at the top of the file, and that will `sysstr()` the mode.  But this does seem confusing- see D7517 <https://phab.mercurial-scm.org/D7517>.
  
  Ah, so it is. Since this is the only use of open in this file, I've switched to just using `pycompat.open` directly in this location.  I'm also fine with just dropping this change.

REPOSITORY
  rHG Mercurial

CHANGES SINCE LAST ACTION
  https://phab.mercurial-scm.org/D7544/new/

REVISION DETAIL
  https://phab.mercurial-scm.org/D7544

To: spectral, #hg-reviewers
Cc: mharbison72, mercurial-devel