'Load the revision history.'

def load_prereq_history(self, storage, data):

    history = storage.get_document_history(self.locale, self.slug)
    if (history is None):
        data[u'needs'].append((u'document_history', self.normalized_path, {u'revisions': self.revisions}))
    elif (len(history) == 0):
        raise self.SourceError(u'Empty    history    for    document    "%s"', self.normalized_path)
