Too many requests error when downloading images on staging

[yinanazhou]

Example error message:

Failed to download image from http://commons.wikimedia.org/wiki/Special:FilePath/Zhongruan.jpg: 429 Client Error: Too many requests - please contact noc@wikimedia.org to discuss a less disruptive approach (0c640b1) for url: https://upload.wikimedia.org/wikipedia/commons/9/90/Zhongruan.jpg