Handle error with non existing template file

This patch allows to propagate IOError instead of returning
TemplateResource which does not contain property_schema.
It's the second attempt to adopt fix introduced here:
Ib1e09de8c10672312eea09f62a28f0885d98b089.

Change-Id: I45604648e3078f8ec6ba8b87a1c08eb6fca790ae
Closes-Bug: #1394552
Merge "Handle error with non existing template file"