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.
return AssetsBundle(xmlid, files, remains=remains, env=env)
    
    @tools.conditional(
        'xml' not in tools.config['dev_mode'],
        tools.ormcache_context('xmlid', 'options.get("lang", "en_US")', 'css', 'js', 'debug', 'kw.get("async")', 'async_load', keys=("website_id",)),
    )
    def _get_asset(self, xmlid, options, css=True, js=True, debug=False, async_load=False, values=None, **kw):
        if 'async' in kw:
            async_load = kw['async']
        files, remains = self._get_asset_content(xmlid, options)
        asset = self.get_asset_bundle(xmlid, files, remains, env=self.env)
        return asset.to_html(css=css, js=js, debug=debug, async_load=async_load, url_for=(values or {}).get('url_for', lambda url: url))
    @tools.conditional(
        
        
        'xml' not in tools.config['dev_mode'],
        tools.ormcache_context('xmlid', 'options.get("lang", "en_US")', 'css', 'js', 'debug', 'kw.get("async")', 'async_load', keys=("website_id",)),
    )
    def _get_asset_nodes(self, xmlid, options, css=True, js=True, debug=False, async_load=False, values=None, **kw):