tests/test-gendoc-pt_BR.t

py3: send bytes from Rust-created warning patterns

Python code expects bytes in both Python 2 and Python 3, so we should send
bytes.

Differential Revision: https://phab.mercurial-scm.org/D7454

#require docutils gettext

  $ $TESTDIR/check-gendoc pt_BR
  checking for parse errors