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/ir_qweb.py
#
        space = el.getprevious() is not None and el.getprevious().tail or el.getparent().text
        sep = u'\n' + space.rsplit('\n').pop()
        return [
            ast.Assign(
                targets=[ast.Name(id='nodes', ctx=ast.Store())],
                value=ast.Call(
                    func=ast.Attribute(
                        value=ast.Name(id='self', ctx=ast.Load()),
                        attr='_get_asset_nodes',
                        ctx=ast.Load()
                    ),
                    args=[
                        ast.Str(el.get('t-call-assets')),
                        ast.Name(id='options', ctx=ast.Load()),
                    ],
                    keywords=[
                        ast.keyword('css', self._get_attr_bool(el.get('t-css', True))),
                        ast.keyword('js', self._get_attr_bool(el.get('t-js', True))),
                        ast.keyword('debug', ast.Call(
                            func=ast.Attribute(
                                value=ast.Name(id='values', ctx=ast.Load()),
                                attr='get',
                                ctx=ast.Load()
                            ),
                            args=[ast.Str('debug')],