private static Field getField(Class<?> clazz, String name) {
      try {
        Field f = clazz.getDeclaredField(name);
        f.setAccessible(true);
        return f;
      } catch (Throwable t) {
        return null;
      }
    }
Unwraps Calcite Invocation exceptions coming meta data provider chain and
obtains the real cause.

@param e
ql/src/java/org/apache/hadoop/hive/ql/parse/CalcitePlanner.java