According document of 'What’s New In Python 3.7', 'async' are reserved keywords now.

Code in line 105 of 'odoo/addons/base/ir/ir_qweb/assetsbundle.py' 
`def to_html(self, sep=None, css=True, js=True, debug=False, async=False, url_for=(lambda url: url)):`
will throw SyntaxError out if we launch odoo with this update python.
""" render(id_or_xml_id, values, **options)
        Render the template specified by the given name.
        :param id_or_xml_id: name or etree (see get_template)
        :param dict values: template values to be used for rendering
        :param options: used to compile the template (the dict available for the rendering is frozen)
            * ``load`` (function) overrides the load method
            * ``profile`` (float) profile the rendering (use astor lib) (filter
              profile line with time ms >= profile)
        """
        for method in dir(self):
            if method.startswith('render_'):
                _logger.warning("Unused method '%s' is found in ir.qweb." % method)
        context = dict(self.env.context, dev_mode='qweb' in tools.config['dev_mode'])
        context.update(options)
        return super(IrQWeb, self).render(id_or_xml_id, values=values, **context)
    def default_values(self):