With Salt 2015.5.1: [Error ] Failed to persist the updated schedule

Leaving this here so I don't forget that the issue exists while I drop back to 2014.

For whatever reason, when running 'sudo minion-sim --count=8' (count is irrelevant, just giving an example), the message in the title pops up once for each minion. Here's a link to the location in the current saltstack github repo where that message emanates from: https://github.com/saltstack/salt/blob/develop/salt/utils/schedule.py#L347

There's a lot there, looks like either that fopen is failing, the write operation is failing, or something about yaml.dump isn't working out. I confirmed that the directory <>/minion.d exists for all the minions, but the _schedule.conf file does not. I tried creating a _schedule.conf file myself, that doesn't seem to change the behavior at all.

Reproduce the report with `sudo minion-sim --count=8`, then inspect `salt/utils/schedule.py` around line 347, where the persistence error is reported. Check the file-open, write, and YAML-dump paths described in the issue; done means the updated schedule persists without the error for the minions.

Written by the indexing model from the issue text.