Comment 4 for bug 1408035

I think this is a duplicate of the following bugs:

https://bugs.launchpad.net/heat/+bug/1407392
https://bugs.launchpad.net/heat/+bug/1407100
https://bugs.launchpad.net/heat/+bug/1407877
https://bugs.launchpad.net/heat/+bug/1401317

I've posted some patches which fix the problem in heat, they're not yet merged:

https://review.openstack.org/#/c/144766/

The problem is we introduced validation which checks the nested template is valid, but we don't want to validate the values at validation (pre-create) time, because indirect references to resources which haven't yet been created may provide invalid values.

A workaround would be to move the RandomString resource inside the nested template, but we should merge the fix to heat soon.