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.
self._append(ast.Name(id='tagName', ctx=ast.Load())),
                ] + self._append_attributes() + [
                    ast.If(
                        test=ast.BoolOp(
                            op=ast.And(),
                            values=[
                                ast.UnaryOp(ast.Not(), ast.Name(id='content', ctx=ast.Load()), lineno=0, col_offset=0),
                                ast.Compare(
                                    left=ast.Name(id='tagName', ctx=ast.Load()),
                                    ops=[ast.In()],
                                    comparators=[ast.Attribute(
                                        value=ast.Name(id='self', ctx=ast.Load()),
                                        attr='_void_elements',
                                        ctx=ast.Load()
                                    )]
                                ),
                            ]
                        ),
                        body=[self._append(ast.Str(u'/>'))],
                        orelse=[
                            self._append(ast.Str(u'>')),
                            ast.If(
                                test=ast.Name(id='content', ctx=ast.Load()),
                                body=[self._append(ast.Name(id='content', ctx=ast.Load()))],
                                orelse=[]
                            ),
                            self._append(ast.Str(u'</')),
                            self._append(ast.Name(id='tagName', ctx=ast.Load())),
                            self._append(ast.Str(u'>')),
                        ]