Check that a statement correctly mentiones that it raises an exception

[JSAbrahams]

Current Issue

148 and to a lesser extent #149

High-level description of the feature

In the language, any statement that may raise an exception must explicitly state so: <statement or expression> raises [<Errors>]

Description of potential implementation

Check that said expression or statement indeed does raise a said exception by looking at the signature of said function.

We also may have to look at the signatures of built-in functions, i.e. division can also throw an arithmetic error: ZeroDivisionError. It would however also need to apply type sensitive flow here, i.e. if we beyond a doubt know that the denominator cannot be 0 we know for sure that this error will not be raised.

[JSAbrahams]

I believe this has been implemented, but more tests should be added to be sure.