cylc/cylc — pull request #513 by hjoliver (2013-06-07 04:50:41+00:00)
Title: Fail self-dependence loops in validation.

Result from the example in #512:

```
$ cylc val bar
Self-dependence detected in 'Task':
line: InitializeTask => ColdTask & InitializeTask & Task
from: InitializeTask => TaskSubset
'ERROR: self-dependence loop detected'```

@trwhitcomb & @matthewrmshin - please review.