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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 ensure_exists(self):
 """ Make sure the local repository exists. :raises: :exc:`~exceptions.ValueError` when the local repository doesn't exist yet. """

        if not self.exists:
            msg = "The local %s repository %s doesn't exist!"
            raise ValueError(msg % (self.friendly_name, format_path(self.local)))