'Print the message to stderr, it will be prefixed with \'WARNING:\'
If stderr is a tty file the \'WARNING:\' will be colored'

def report_warning(self, message):

    if (self.params.get(u'logger') is not None):
        self.params[u'logger'].warning(message)
    else:
        if self.params.get(u'no_warnings'):
            return
        if ((not self.params.get(u'no_color')) and self._err_file.isatty() and (compat_os_name != u'nt')):
            _msg_header = u'\x1b[0;33mWARNING:\x1b[0m'
        else:
            _msg_header = u'WARNING:'
        warning_message = (u'%s    %s' % (_msg_header, message))
        self.to_stderr(warning_message)
