Resolves #2

[davidyell]

Added missing exception class

[ADmad]

Can you please add test which triggers this exception.

[davidyell]

I'd love to, but there aren't any tests to go on. I'd feel happier extending existing tests to ensure that the code formatting was similar.

I'll try and write up a test for it, if I can get some time.

[ADmad]

Give it a shot and ask for pointers if you get stuck. In general check core for how exception throwing from a method is tested.

[steefaan]

Maybe you should merge this and do the test cases with a separate PR. Currently you get a Fatal Error because the class is missing. This would solve at least this bad issue.

[davidyell]

It would be handy, as I've just been given a huge project at work, so will not have much time to work on this. I can try and find some time in the evenings, but it's a long shot.

[jadb]

I agree @steefaan but giving a hand to @davidyell wouldn't have hurt ;)