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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 check_for_wkhtmltohtml():
 """ Checks to see if the wkhtmltohtml binary is installed. Raises error if not. """

    locator = 'where' if sys.platform == 'win32' else 'which'

    wkhtmltopdf = (subprocess.Popen([locator, 'wkhtmltopdf'],
                                    stdout=subprocess.PIPE)
                   .communicate()[0].strip())

    if not os.path.exists(wkhtmltopdf):
        logging.error(
            'No wkhtmltopdf executable found. Please install '
            'wkhtmltopdf before trying again - {}'.format(WKHTMLTOPDF_URL))
        raise ValueError(
            'No wkhtmltopdf executable found. Please install '
            'wkhtmltopdf before trying again - {}'.format(WKHTMLTOPDF_URL))