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.
keywords=[], starargs=None, kwargs=None
                        )),
                        ast.keyword('async', self._get_attr_bool(el.get('async', False))),
                        ast.keyword('values', ast.Name(id='values', ctx=ast.Load())),
                    ],
                    starargs=None, kwargs=None
                )
            ),
            ast.For(
                target=ast.Tuple(elts=[
                    ast.Name(id='index', ctx=ast.Store()),
                    ast.Tuple(elts=[
                        ast.Name(id='tagName', ctx=ast.Store()),
                        ast.Name(id='t_attrs', ctx=ast.Store()),
                        ast.Name(id='content', ctx=ast.Store())
                    ], ctx=ast.Store())
                ], ctx=ast.Store()),
                iter=ast.Call(
                    func=ast.Name(id='enumerate', ctx=ast.Load()),
                    args=[ast.Name(id='nodes', ctx=ast.Load())],
                    keywords=[],
                    starargs=None, kwargs=None
                ),
                body=[
                    ast.If(
                        test=ast.Name(id='index', ctx=ast.Load()),
                        body=[self._append(ast.Str(sep))],
                        orelse=[]
                    ),
                    self._append(ast.Str(u'<')),