pig/src/main/java/com/twitter/elephantbird/pig/util/PigUtil.java
public static Class<? extends Message> getProtobufClass(String protoClassName) {
    try {
      // try Pig's loader
      Class<?> protoClass = getClass(protoClassName);
      return protoClass.asSubclass(Message.class);
    } catch (RuntimeException e) {
      // try normal loader first (handles inner class).
      return Protobufs.getProtobufClass(protoClassName);
    }
  }
public static Class<? extends Message> getProtobufClass(String protoClassName) {
    try {
      // try Pig's loader
      Class<?> protoClass = getClass(protoClassName);
      return protoClass.asSubclass(Message.class);
    } catch (RuntimeException e) {
      // try normal loader first (handles inner class).
      return Protobufs.getProtobufClass(protoClassName);
    }
  }
Returns class using Pig's class loader.
If that fails tries {@link Protobufs#getProtobufClass(String)} to
resolve the class