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/tools/safe_eval.py
if globals is None:
        globals = {}
    if locals is None:
        locals = {}
    if fromlist is None:
        fromlist = []
    if name in _ALLOWED_MODULES:
        return __import__(name, globals, locals, level)
    raise ImportError(name)
_BUILTINS = {
    '__import__': _import,
    'True': True,
    'False': False,
    'None': None,
    'bytes': bytes,
    'str': str,
    'unicode': pycompat.text_type,