rust-filepatterns: fix type of warnings tuple to (bytes, bytes) Otherwise warn() in match.py would fail if the warning contains non-ASCII character. We might want to add a thin ByteString wrapper around Vec<u8> to implement ToPyObject<ObjectType = PyBytes>, but I'm not sure.

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

  $ hg init

  $ echo 'base' > base
  $ hg ci -Ambase
  adding base

  $ hg qnew -mmqbase mqbase

  $ hg qsave
  $ hg qrestore 2
  restoring status: hg patches saved state