To reproduce, run any program on Linux with DISPLAY set to the empty string:

    DISPLAY="" java -jar Ensemble.jar

Now that RT-37974 is implemented, an exception will be thrown in the case of no valid DISPLAY. Before that expected exception is thrown, the prism-es2 pipeline prints the following warning:

"Failed in XOpenDisplay"

This is especially noticeable when running the unit tests (gradle -PFULL_TEST=true test)

We should not print a warning message to the console. The warning message should be removed or qualified with "prism.verbose".