How to get Spark Interpreter working with custom python configuration

[#1]

Change the livy.spark.master to yarn cluster and add the following environment variable in the zeppelin-env from ambari

export PYSPARK_DRIVER_PYTHON=path_to_python2.7 
export PYSPARK_PYTHON=path_to_python2.7 

After this restart livy spark interpreter started to work.

[#2]

Why are we changing it in the Zeppelin env? Can this be changed in the Spark interpreter configs? /cc @prabhjyot singh

[#3]

Does this work with Zeppelin 0.7.0?