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
"""safe_eval(expression[, globals[, locals[, mode[, nocopy]]]]) -> result
    System-restricted Python expression evaluation
    Evaluates a string that contains an expression that mostly
    uses Python constants, arithmetic expressions and the
    objects directly provided in context.
    This can be used to e.g. evaluate
    an OpenERP domain expression from an untrusted source.
    :throws TypeError: If the expression provided is a code object
    :throws SyntaxError: If the expression provided is not valid Python
    :throws NameError: If the expression provided accesses forbidden names
    :throws ValueError: If the expression provided uses forbidden bytecode
    """
    if type(expr) is CodeType:
        raise TypeError("safe_eval does not allow direct evaluation of code objects.")
    
    
    if not nocopy: