HADOOP-17120. Fix failure of docker image creation due to pip2 install error. (#2130)

(cherry picked from commit 53cfe6090419649dde18e3bf0d6ff757f76d716f)

dev-support/docker/Dockerfile

@@ -168,7 +168,8 @@ RUN apt-get -q update \
 ####
 RUN pip2 install \
     configparser==4.0.2 \
-    pylint==1.9.2
+    pylint==1.9.2 \
+    isort==4.3.21
 
 ####
 # Install dateutil.parser