Not a very useful error message "Message:Error generating canonicalized entry"

[sylvestre]

This is probably an issue on my side but the error message isn't helpful for me to debug

$ rekor upload --rekor_server https://rekor.sigstore.dev --signature llvm-toolchain-12_12.0.1~+rc4-1_amd64.changes  --public-key /tmp/a.key --artifact llvm-toolchain-12_12.0.1~+rc4-1_amd64.changes
2021/07/10 09:40:05 [POST /api/v1/log/entries][500] createLogEntry default  &{Code:500 Message:Error generating canonicalized entry}

Seems to be coming from:

rekor/pkg/api/entries.go

Lines 138 to 141 in 9fa4e20

	leaf, err := entry.Canonicalize(ctx)
	if err != nil {
	return nil, handleRekorAPIError(params, http.StatusInternalServerError, err, failedToGenerateCanonicalEntry)
	}