stop charging failed cards

[chadwhitacre]

Closes #3531.

[chadwhitacre]

I think the fix for this is actually pretty trivial, simply constraining the participants query in payday.sql with AND error = ''. We should have a test, though, and I don't see that we demonstrate the working case first yet.

[chadwhitacre]

@rohitpaulk Looks like you accidentally committed gratipay.{js,css}, ya?

[rohitpaulk]

Ah, right. Force pushing that off...

[chadwhitacre]

I'm good to merge (once Travis is green) if you're okay with 8a6f517.

[chadwhitacre]

Interesting, I'm not seeing that locally.

[chadwhitacre]

/me runs a full make test

[chadwhitacre]

Hrm ... I now get the error Travis gets, plus a bonus error. O.O

[chadwhitacre]

___________________________ TestNewTeams.test_migrate_tips_to_subscriptions ____________________________
Traceback (most recent call last):
  File "/Users/whit537/personal/gratipay/gratipay.com/tests/py/test_teams.py", line 133, in test_migrate_tips_to_subscriptions
    assert subscriptions[0].subscriber == 'alice'
AssertionError: assert 'bob' == 'alice'
  - bob
  + alice

[chadwhitacre]

Gah, the Travis error is because my commit was bad, one sec ...