'Prompt the user for a path.
:param str label: The user-friendly label for the file.
:param callable validator: A method which will be called to validate the supplied input
after it has been validated to be a non-empty path to an existing file. Should throw a
`~certbot.errors.PluginError` to indicate any issue.
:returns: The user\'s response (guaranteed to exist).
:rtype: str'

@staticmethod
def _prompt_for_file(label, validator=None):

    def __validator(filename):
        if (not filename):
            raise errors.PluginError('Please    enter    a    valid    path    to    your    {0}.'.format(label))
        filename = os.path.expanduser(filename)
        validate_file(filename)
        if validator:
            validator(filename)
    (code, response) = ops.validated_directory(__validator, 'Input    the    path    to    your    {0}'.format(label), force_interactive=True)
    if (code == display_util.OK):
        return response
    else:
        raise errors.PluginError('{0}    required    to    proceed.'.format(label))
