Create and raise module-defined exceptions

**Is your feature request related to a problem? Please describe.**
I would like to catch module-level exceptions.

**Describe the solution you'd like**
The general Python solution here is to create a module-level exception class that is subclassed throughout the code. The interface should define what exceptions could be raised. The caller can then catch/handle these exceptions.

**Describe alternatives you've considered**
I currently use 'except Exception...' which is not good.