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.
field_options['template_options'] = options
        field_options['type'] = field_options['widget']
        field_options['tagName'] = tagName
        field_options['expression'] = expression
        
        model = 'ir.qweb.field.' + field_options['type']
        converter = self.env[model] if model in self.env else self.env['ir.qweb.field']
        
        content = converter.value_to_html(value, field_options)
        attributes = OrderedDict()
        attributes['data-oe-type'] = field_options['type']
        attributes['data-oe-expression'] = field_options['expression']
        return (attributes, content, None)
    
    def _compile_expr(self, expr):