def METHOD_NAME(self):
    """Get version from `gunicorn --version`"""
    cmd = '{} --version'.format(self.gunicorn_cmd)
    try:
        pc_out, pc_err, _ = get_subprocess_output(cmd, self.log, False)
    except OSError:
        self.log.debug("Error collecting gunicorn version.")
        return None
    match = re.match(self.VERSION_PATTERN, pc_out)
    if not match:
        match = re.match(self.VERSION_PATTERN, pc_err)
    if match:
        return match.groups()[0]
    else:
        self.log.debug("Version not found in stdout `%s` and stderr `%s`", pc_out, pc_err)
    return None