code: private ProtoNetwork failProteinFamilies(final ProtoNetwork pn,
              final StringBuilder bldr, String pfLocation, String errorMessage) {
          bldr.append("PROTEIN FAMILY RESOLUTION FAILURE in ");
          bldr.append(pfLocation);
          bldr.append("\n\treason: ");
          bldr.append(errorMessage);
          stageWarning(bldr.toString());
  
          // could not resolve protein family resource so return original
          // proto network.
          return pn;
      }
docs: Logic to recover from a failed protein family document.
  
  @param pn
  @param bldr
  @param pfLocation
  @param e
  @return