Use argparse to setup spark (jupyter#2082)

Author: mathbunnyru

images/pyspark-notebook/Dockerfile

@@ -41,11 +41,11 @@ ENV SPARK_OPTS="--driver-java-options=-Xms1024M --driver-java-options=-Xmx4096M
 COPY setup_spark.py /opt/setup-scripts/
 
 # Setup Spark
-RUN SPARK_VERSION="${spark_version}" \
-    HADOOP_VERSION="${hadoop_version}" \
-    SCALA_VERSION="${scala_version}" \
-    SPARK_DOWNLOAD_URL="${spark_download_url}" \
-    /opt/setup-scripts/setup_spark.py
+RUN /opt/setup-scripts/setup_spark.py \
+    --spark-version="${spark_version}" \
+    --hadoop-version="${hadoop_version}" \
+    --scala-version="${scala_version}" \
+    --spark-download-url="${spark_download_url}"
 
 # Configure IPython system-wide
 COPY ipython_kernel_config.py "/etc/ipython/"