TP build errors

[dangogh]

Traffic Portal fails to build in https://builds.apache.org/view/S-Z/view/TrafficControl/job/trafficcontrol-master-build apparently due to an upstream change:

Step 6/9 : RUN    gem update --system &&     gem install rb-inotify -v 0.9.10 &&     gem install compass &&     npm -g install bower grunt-cli
 ---> Running in 466b8eb0e5a5
ERROR:  Error installing rubygems-update:
    rubygems-update requires Ruby version >= 2.3.0.
ERROR:  While executing gem ... (NoMethodError)
    undefined method `version' for nil:NilClass
Updating rubygems-update
ERROR: Service 'traffic_portal_build' failed to build: The command '/bin/sh -c gem update --system &&     gem install rb-inotify -v 0.9.10 &&     gem install compass &&     npm -g install bower grunt-cli' returned a non-zero code: 1