stores content in cache. 'cachekey' must be the same key as returned from checkCache().
        Returns the content.

def writeCache(self, cachekey, content):
        """stores content in cache. 'cachekey' must be the same key as returned from checkCache().
        Returns the content."""
        self.rendercache[cachekey] = content
        try:
            open(cachekey, 'w').write(content)
        except:
            print("Error writing cache file", cachekey, ", will regenerate next time")
            traceback.print_exc()
        return content