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.
odoo/addons/base/ir/ir_qweb/assetsbundle.py
if self._id is None: self._id = str(uuid.uuid4())
        return self._id
    @func.lazy_property
    def name(self):
        name = '<inline asset>' if self.inline else self.url
        return "%s defined in bundle '%s'" % (name, self.bundle.name)
    @property
    def html_url(self):
        return self.html_url_format % self.html_url_args
    def stat(self):
        if not (self.inline or self._filename or self._ir_attach):
            path = (segment for segment in self.url.split('/') if segment)
            self._filename = get_resource_path(*path)
            if self._filename:
                return
            try:
                
                fields = ['__last_update', 'datas', 'mimetype']
                domain = [('type', '=', 'binary'), ('url', '=', self.url)]
                attach = self.bundle.env['ir.attachment'].sudo().search_read(domain, fields)
                self._ir_attach = attach[0]
            except Exception:
                raise AssetNotFound("Could not find %s" % self.name)
    
    def to_html(self):