api/metadata: third time's the charm

Signed-off-by: William Woodruff <william@trailofbits.com>

Author: woodruffw

tuf/api/metadata.py

@@ -443,7 +443,7 @@ def verify_delegate(
                 key.verify_signature(delegated_metadata, signed_serializer)
                 signing_keys.add(key.keyid)
             except exceptions.UnsignedMetadataError:
-                logger.warning(
+                logger.debug(
                     "Key %s failed to verify %s", keyid, delegated_role
                 )
 
@@ -778,7 +778,9 @@ def verify_signature(
             SerializationError,
         ) as e:
             # Log unexpected failure, but continue as if there was no signature
-            logger.debug("Key %s failed to verify sig: %s", self.keyid, str(e))
+            logger.warning(
+                "Key %s failed to verify sig: %s", self.keyid, str(e)
+            )
             raise exceptions.UnsignedMetadataError(
                 f"Failed to verify {self.keyid} signature"
             ) from e