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.
raise
    except odoo.http.AuthenticationError:
        raise
    except OperationalError:
        
        
        raise
    except odoo.exceptions.MissingError:
        raise
    except Exception as e:
        exc_info = sys.exc_info()
        pycompat.reraise(ValueError, ValueError('%s: "%s" while evaluating\n%r' % (ustr(type(e)), ustr(e), expr)), exc_info[2])
def test_python_expr(expr, mode="eval"):
    try:
        test_expr(expr, _SAFE_OPCODES, mode=mode)
    except (SyntaxError, TypeError, ValueError) as err:
        if len(err.args) >= 2 and len(err.args[1]) >= 4:
            error = {
                'message': err.args[0],
                'filename': err.args[1][0],
                'lineno': err.args[1][1],
                'offset': err.args[1][2],
                'error_line': err.args[1][3],
            }
            msg = "%s : %s at line %d\n%s" % (type(err).__name__, error['message'], error['lineno'], error['error_line'])
        else:
            msg = ustr(err)
        return msg
    return False