Add better inconsistency reporting on input data

If the concatenation of the input data fails, it can be difficult to figure out what the problem is. It would be nice to make it easy to identify the problems.

The aim here is to provide a catchall informative "error message" that explains why the data could not be concatenated. I.e. to avoid the very uninformative error message that Iris (at least in 2.2) issues.