void checkOutputSpec(BaseWork work, JobConf jc) throws IOException {
    for (Operator<?> op : work.getAllOperators()) {
      if (op instanceof FileSinkOperator) {
        ((FileSinkOperator) op).checkOutputSpecs(null, jc);
      }
    }
  }
Ensures that the Tez Session is open and the AM has all necessary jars configured.
ql/src/java/org/apache/hadoop/hive/ql/exec/tez/TezTask.java