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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def parse_url(url):
 """ Parse the given url and update it with environment value if required. :param basestring url: :rtype: basestring :raise: KeyError if environment variable is needed but not found. """

    # the url has to be a unicode by pystache's design, but the unicode concept has been rewamped in py3
    # we use a try except to make the code compatible with py2 and py3
    try:
        url = unicode(url)
    except NameError:
        url = url

    parsed = pystache.parse(url)
    # pylint: disable=protected-access
    variables = (element.key for element in parsed._parse_tree if isinstance(element, _EscapeNode))
    return pystache.render(url, {variable: os.environ[variable] for variable in variables})