Launch the process and return the process object.

def _launch(self, run_config, args, **kwargs):
    """Launch the process and return the process object."""
    del kwargs
    try:
      with sw("popen"):
        return subprocess.Popen(args, cwd=run_config.cwd, env=run_config.env)
    except OSError:
      logging.exception("Failed to launch")
      raise SC2LaunchError("Failed to launch: %s" % args)