Start EG in demo-image to inherit PYSPARK_PYTHON env (#1230)

Author: kevin-bates

etc/docker/enterprise-gateway-demo/start-enterprise-gateway.sh.template

@@ -21,6 +21,7 @@ echo "Starting Jupyter Enterprise Gateway..."
 
 jupyter enterprisegateway \
 	--log-level=${EG_LOG_LEVEL} \
+	--EnterpriseGatewayApp.inherited_envs=PYSPARK_PYTHON \
 	--MappingKernelManager.cull_idle_timeout=${EG_CULL_IDLE_TIMEOUT} \
 	--MappingKernelManager.cull_interval=30 \
 	--MappingKernelManager.cull_connected=${EG_CULL_CONNECTED} 2>&1 | tee /usr/local/share/jupyter/enterprise-gateway.log