code: public String getIssuerName(String defaultName) {
          return (cert == null ? defaultName
                               : cert.getIssuerX500Principal().toString());
      }
docs: return string form of issuer name from certificate associated with this
  build step, or a default name if no certificate associated with this
  build step, or if issuer name could not be obtained from the certificate.
  
  @param defaultName name to use as default if unable to return an issuer
  name from the certificate, or if no certificate.
  @returns String form of issuer name or defaultName, if no certificate or
  exception received while trying to extract issuer name from certificate.