code: private List<MigrationInfo> failed(MigrationInfo[] migrationInfos) {
          if (migrationInfos.length == 0)
              throw new NotFoundException();
          List<MigrationInfo> failedMigrations = Lists.newArrayList();
          for (MigrationInfo migrationInfo : migrationInfos) {
              if (migrationInfo.getState().isFailed()) {
                  failedMigrations.add(migrationInfo);
              }
          }
  
          return failedMigrations;
      }
docs: Retrieves the full set of infos about the migrations that failed.
  
  @return The failed migrations. An empty array if none.