factory: return wrapped errors instead of panics

General MR

Summary

Replace the HandleError invocations in the factory and fake_factory code to return wrapped errors instead of resulting in a panic. Update the unit tests to test the new error logic.

The coverage was a little inflated since many of the error cases were passed to HandleError, which is called in both happy and error paths, so handling the errors in this new manner creates some gaps. I've tried to force errors where I can on the factory but the last few points will be very difficult I think.

Relevant logs/screenshots

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Linked Issue

closes #179 (closed)

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