code: public static String missingFieldName(ScmPluginException e) {
          if (isFieldMissing(e)) {
              return ((ScmUserInfoMissing) e).getFieldName();
          }
          return null;
      }
docs: Returns the missing field name if the exception is a {@link ScmUserInfoMissing}
  
  @param e exception
  
  @return missing field name, or null