[clang] [libclang/python] Improve error reporting of `TranslationUnit` creating functions (PR #102410)

[Vlad Serebrennikov via cfe-commits]

Endilll wrote:

Heads up: this will be closed in favor of #182843 when it's merged, because it addresses our concerns about error handling much better.

https://github.com/llvm/llvm-project/pull/102410