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
self.name = name
        self.env = request.env if env is None else env
        self.max_css_rules = self.env.context.get('max_css_rules', MAX_CSS_RULES)
        self.javascripts = []
        self.stylesheets = []
        self.css_errors = []
        self._checksum = None
        self.files = files
        for f in files:
            if f['atype'] == 'text/sass':
                self.stylesheets.append(SassStylesheetAsset(self, url=f['url'], filename=f['filename'], inline=f['content'], media=f['media']))
            elif f['atype'] == 'text/less':
                self.stylesheets.append(LessStylesheetAsset(self, url=f['url'], filename=f['filename'], inline=f['content'], media=f['media']))
            elif f['atype'] == 'text/css':
                self.stylesheets.append(StylesheetAsset(self, url=f['url'], filename=f['filename'], inline=f['content'], media=f['media']))
            elif f['atype'] == 'text/javascript':
                self.javascripts.append(JavascriptAsset(self, url=f['url'], filename=f['filename'], inline=f['content']))
    
    def to_html(self, sep=None, css=True, js=True, debug=False, async_load=False, url_for=(lambda url: url), **kw):
        if 'async' in kw:
            _logger.warning("Using deprecated argument 'async' in to_html call, use 'async_load' instead.")
            async_load = kw['async']
        nodes = self.to_node(css=css, js=js, debug=debug, async_load=async_load)
        if sep is None:
            sep = u'\n            '
        response = []
        for tagName, attributes, content in nodes:
            html = u"<%s " % tagName
            for name, value in attributes.items():
                if value or isinstance(value, string_types):