Update Dockerfile

Dockerfile

@@ -43,7 +43,7 @@ RUN useradd -m -s /bin/bash -N -u $NB_UID $NB_USER && \
     chown $NB_USER / && \
     chpasswd $NB_USER:ar-noc
 RUN usermod -aG docker ${NB_USER}
-
+.
 USER $NB_USER
 
 ARG python_version=3.6