In codecs.c there is a call to _PyErr_TrySetFromCause (a function that is only called from here), which tries to create a new exception of the same type with a different message, but bails out if there are any complications that make this unsafe. The purpose is to add information about the context of the operation that failed, without changing the type of the exception. This can be solved more easily and robustly with PEP-678 exception notes.

Linked PRs

• gh-102406: replace exception chaining by PEP-678 notes in codecs #102407