Genie_python: Refactor the way exceptions are used

As a developer, I don't want generic exception handling to obscure genuine problems.

Currently genie_python uses a lot of `catch Exception as e:`, `catch:`, `raise Exception()` constructs. This is bad because we currently catch things like `MemoryError` (which is obviously not something we can just log and ignore).

Go through the various genie_python files and replace `catch Exception` / `raise Exception` blocks with specific exceptions that we can handle.