improve error

Author: jsha

mtca/mtca.go

@@ -7,6 +7,7 @@ import (
 	"crypto/rand"
 	"crypto/sha256"
 	"crypto/x509"
+	"database/sql"
 	"encoding/asn1"
 	"errors"
 	"fmt"
@@ -431,6 +432,9 @@ func (m *mtca) latest(ctx context.Context) (*checkpoint, error) {
 		m.mtcLogID(),
 		m.mtcLogID())
 	if err != nil {
+		if errors.Is(err, sql.ErrNoRows) {
+			return nil, fmt.Errorf("getting latest checkpoint for %q: issuance log DB is not initialized", m.mtcLogID())
+		}
 		return nil, fmt.Errorf("getting latest checkpoint for %q: %w", m.mtcLogID(), err)
 	}