force the runtim to use python3

redbull/sparklib.py

@@ -60,6 +60,10 @@ def custom_app_cmd(webui_port, app_file_name):
         # kick off start-all spark command as a bg process 
         '($SPARK_HOME/sbin/start-all.sh --webui-port ' + str(webui_port) + ' &)',
 
+        # set the runtim to python 3
+        'export PYSPARK_PYTHON=/usr/bin/python3',
+        'export PYSPARK_DRIVER_PYTHON=python3',
+
         # execute spark-submit on the specified app 
         '$SPARK_HOME/bin/spark-submit ' +
             '--master spark://${AZ_BATCH_MASTER_NODE%:*}:7077 ' +