signer: fix SSlibKey error handling in verify

Key.verify_signature implementations should only raise
UnverifiedSignatureError or VerificationError, even if an optional
dependency is missing.

This commit changes SSlibKey.verify_signature to re-raise
UnsupportedLibrarError as VerificationError.

Signed-off-by: Lukas Puehringer <[email protected]>

Author: lukpueh

securesystemslib/signer/_key.py

@@ -175,6 +175,7 @@ def verify_signature(self, signature: Signature, data: bytes) -> None:
             exceptions.CryptoError,
             exceptions.FormatError,
             exceptions.UnsupportedAlgorithmError,
+            exceptions.UnsupportedLibraryError,
         ) as e:
             logger.info("Key %s failed to verify sig: %s", self.keyid, str(e))
             raise exceptions.VerificationError(