Fix pyarrow install

Need to install as NB_UID, not root, to keep all /opt/conda
folders writeable by the default user

pyspark-notebook/Dockerfile

@@ -15,11 +15,6 @@ RUN apt-get -y update && \
     apt-get clean && \
     rm -rf /var/lib/apt/lists/*
 
-# Install pyarrow
-RUN conda install --quiet -y 'pyarrow' && \
-    fix-permissions $CONDA_DIR && \
-    fix-permissions /home/$NB_USER
-
 RUN cd /tmp && \
         wget -q http://apache.claz.org/spark/spark-${APACHE_SPARK_VERSION}/spark-${APACHE_SPARK_VERSION}-bin-hadoop${HADOOP_VERSION}.tgz && \
         echo "258683885383480BA01485D6C6F7DC7CFD559C1584D6CEB7A3BBCF484287F7F57272278568F16227BE46B4F92591768BA3D164420D87014A136BF66280508B46 *spark-${APACHE_SPARK_VERSION}-bin-hadoop${HADOOP_VERSION}.tgz" | sha512sum -c - && \
@@ -45,3 +40,8 @@ ENV MESOS_NATIVE_LIBRARY /usr/local/lib/libmesos.so
 ENV SPARK_OPTS --driver-java-options=-Xms1024M --driver-java-options=-Xmx4096M --driver-java-options=-Dlog4j.logLevel=info
 
 USER $NB_UID
+
+# Install pyarrow
+RUN conda install --quiet -y 'pyarrow' && \
+    fix-permissions $CONDA_DIR && \
+    fix-permissions /home/$NB_USER