Error handling in kleopatra is bad in serveral cases.
I think the best way for this would be to have libkleo parse decryption and verification results and use them in Kleopatra.
- Clipboard decrypt/verify without secret key for message results in "No signature found"
- File decryption without secret key results in "Decryption Failed: Decryption Failed."
There's probably a lot more where that came from.