code: @Override
      public String getMessage() {
          StringBuilder builder = new StringBuilder( super.getMessage() );
          for( LessFilePosition pos : positions ) {
              builder.append( "\n\t on line " ).append( pos.getLine() ).append( ", column " ).append( pos.getColumn() );
              if( pos.getFilename() != null ) {
                  builder.append( ", file " ).append( pos.getFilename() );
              }
          }
          return builder.toString();
      }
docs: The message plus the less file stacktrace.
  {@inheritDoc}