Resolving 'Can't connect to window server - not enough permissions' forMaven test runs

Our CI server (we use Jenkins) recently began bombing on several new tests that referenced java.awt packaged classes. The most common error in the stacktrace was "NoClassDefFoundError: Could not initialize class java.awt.Color" and diving deeper we could see the root cause was "Can't connect to window server - not enough permissions".
The interwebs all claimed setting -Djava.awt.headless=true would resolve the issue but it did nothing for us. We set it as a Jenkins system parameter, in the launchctl job, in the bash_profile of the Jenkins user on the machine, and everywhere we could in the Jenkins job no avail.
Just before heading down the path of setting it programatically somewhere in our test stack - I noticed that our maven-surefire-plugin was configured to use a threadCount of 10. On a hunch that maven-surefire-plugin was not exporting my system properties to the new threads it spawned for the test run - I configured the plugin to set java.awt.headless with the following snip from our pom.xml

Problem solved.