More details on situations where this has been needed for certain types of bots are in https://github.com/luci/luci-py/issues/277 .

It just occurred to me that this is trivially implementable on the bot side via bot_config.py on_after_task().

- If BOT_DIED occurred in two successive tasks, self-quarantine  (this could eventually be upgraded to first occurence)
- If task failure N successive tasks, self-quarantine

This can be done with two global variable.

The state will reset whenever bot_main is restarted:
- bot_config update (new luci-config push)
- bot_code update (new server push)
- host rebooted

This also gives an easy way to "mass reset" the state, which is a good thing. This will help with bugs like issue 766877.

Removing issue 757931 as a blocker.

The following revision refers to this bug:
  https://chrome-internal.googlesource.com/infradata/config/+/8c58dd05c19ef920ddbf7dc02211e0ab6f859f29

commit 8c58dd05c19ef920ddbf7dc02211e0ab6f859f29
Author: Marc-Antoine Ruel <maruel@chromium.org>
Date: Fri Nov 03 20:24:30 2017

The following revision refers to this bug:
  https://chrome-internal.googlesource.com/infradata/config/+/fdbdf8fa9895c9aa66cc989eeaf7a25fb2d54cd6

commit fdbdf8fa9895c9aa66cc989eeaf7a25fb2d54cd6
Author: Marc-Antoine Ruel <maruel@chromium.org>
Date: Fri Nov 10 19:07:00 2017