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.
"""Improve and remove sensitive information from sass/less compilator error messages"""
        error = misc.ustr(stderr).split('Load paths')[0].replace('  Use --trace for backtrace.', '')
        if 'Cannot load compass' in error:
            error += "Maybe you should install the compass gem using this extra argument:\n\n" \
                     "    $ sudo gem install compass --pre\n"
        error += "This error occured while compiling the bundle '%s' containing:" % self.name
        for asset in self.stylesheets:
            if isinstance(asset, PreprocessedCSS):
                error += '\n    - %s' % (asset.url if asset.url else '<inline sass>')
        return error
class WebAsset(object):
    html_url_format = '%s'
    _content = None
    _filename = None
    _ir_attach = None
    _id = None
    def __init__(self, bundle, inline=None, url=None, filename=None):
        self.bundle = bundle
        self.inline = inline
        self._filename = filename
        self.url = url
        self.html_url_args = url
        if not inline and not url:
            raise Exception("An asset should either be inlined or url linked, defined in bundle '%s'" % bundle.name)
    @func.lazy_property
    def id(self):