Description

When SCT verification fails, the error printed is:

Error: signing {blob-name-here}: getting key from Fulcio: verifying SCT: error verifying embedded SCT
main.go:74: error during command execution: signing to-sign: getting key from Fulcio: verifying SCT: error verifying embedded SCT

The verification can fail because of multiple different issues and the current error message doesn't provide any details to help debugging. It would be great to include the underlying verification error in the message to improve this. I'll submit a PR shortly to fix this.