+ smut who did refactoring in API handlers.

> Login failed or canceled.

That doesn't look right... Can you run 'auth.py login' with '-v -v' flags to get more logging?

To fix:
1. Try to logout first using "auth.py logout --service=https://isolateserver.appspot.com". Then login again.
2. If it doesn't help, try "auth.py login --auth-no-local-webserver --service=https://isolateserver.appspot.com" (maybe there are issues with opening the browser on Windows).

E:\src\chrome2\src>python tools/swarming_client/auth.py login --service=https://chromium-swarm.appspot.com -v -v
Login failed or canceled.

E:\src\chrome2\src>python tools/swarming_client/auth.py login -v -v --service=https://chromium-swarm.appspot.com
Login failed or canceled.



E:\src\chrome2\src>python tools/swarming_client/auth.py logout --service=https://isolateserver.appspot.com

E:\src\chrome2\src>python tools/swarming_client/auth.py login --service=https://isolateserver.appspot.com
Login failed or canceled.

E:\src\chrome2\src>python tools/swarming_client/auth.py login --auth-no-local-webserver --service=https://isolateserver.appspot.com
Login failed or canceled.

Hm, it doesn't even attempt to do anything. 

Do you happen to have any of the following env vars set:
  CHROME_HEADLESS
  SWARMING_HEADLESS
  SWARMING_AUTH_SERVICE_ACCOUNT_JSON
  LUCI_CONTEXT
?

Yes, I do have
CHROME_HEADLESS=1
because I was trying to be similar to a bot when I run tests.

Removing that now fixes things, thanks.

Can these scripts print an error if they're not working due to these variables beings set?

I'll add something to auth.py. 

The rest of the script are actually used on bots, where changing behavior on presence of CHROME_HEADLESS is intended, so printing errors there would be incorrect.