cylc/cylc — pull request #699 by hjoliver (2013-09-23 00:40:15+00:00)
Title: Print item keys in IllegalItemError, in sections with __MANY__ items.

```
[runtime]
[[root]]
[[[event hooks]]]
rubbish = garbage
```
Validation should have printed this:
```
'Illegal item: [runtime][root][event hooks]rubbish'
```
but it was printing this:
```
'ERROR: illegal item: rubbish'
```