Expose internal errors.

[jorgii]

Please provide enough information so that others can review your pull request:

This pull request solves exposes the internal errors so that they can be used publicly.

Explain the details for making this change. What existing problem does the pull request solve?

The problem is described in #1375.

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[jorgii]

This is the easy version of the fix, aliasing the internal errors. This brings the potential problem where someone working on the internal error might not realise that they are exposed to the public.
I am pushing this as a start.
This could be improved by moving all the error definitions outside so that it is explicit they are public.

Does that make sense to do?

[ReneWerner87]

yes it makes sense, but because this internal code is a copy, it will be difficult to do so

[jorgii]

Should I try and do the refactor?

[ReneWerner87]

but when we refresh the code we copied, this customization flies out again, so i think the current solution is good

[jorgii]

Alright, making the PR ready for merge.

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