bot_update seems to hang for about 40 minutes, fairly frequently. 

Example log: 
https://luci-logdog.appspot.com/v/?s=chromium%2Fbb%2Fchromium.webkit%2FWebKit_Win_Builder__dbg_%2F105445%2F%2B%2Frecipes%2Fsteps%2Fbot_update%2F0%2Fstdout

It might be related to being run on Windows?

I can get more data about where this happens tomorrow hopefully. 

I've seen this issue several times, and it's happening enough that I think someone should try to take a look.