When a build fails, pybot will never be called because it's not necessary since the build failed. Because of this, there isn't a need to process robotframework reports since the output directory will never exist. So the idea is to not do anything upon a build failure.

Here is the unnecessary exception:
Robot results publisher started...
-Parsing output xml:
Failed!
/var/lib/jenkins/jobs/XXXXX/workspace/my_robot_results does not exist.
at org.apache.tools.ant.types.AbstractFileSet.getDirectoryScanner(AbstractFileSet.java:483)
at org.apache.tools.ant.types.AbstractFileSet.getDirectoryScanner(AbstractFileSet.java:460)
at hudson.plugins.robot.RobotParser$RobotParserCallable.invoke(RobotParser.java:65)
at hudson.plugins.robot.RobotParser$RobotParserCallable.invoke(RobotParser.java:51)
at hudson.FilePath.act(FilePath.java:920)
at hudson.FilePath.act(FilePath.java:893)
at hudson.plugins.robot.RobotParser.parse(RobotParser.java:46)
at hudson.plugins.robot.RobotPublisher.parse(RobotPublisher.java:218)
at hudson.plugins.robot.RobotPublisher.perform(RobotPublisher.java:241)
at hudson.tasks.BuildStepMonitor$1.perform(BuildStepMonitor.java:20)
at hudson.model.AbstractBuild$AbstractBuildExecution.perform(AbstractBuild.java:745)
at hudson.model.AbstractBuild$AbstractBuildExecution.performAllBuildSteps(AbstractBuild.java:709)
at hudson.model.Build$BuildExecution.post2(Build.java:182)
at hudson.model.AbstractBuild$AbstractBuildExecution.post(AbstractBuild.java:658)
at hudson.model.Run.execute(Run.java:1734)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:43)
at hudson.model.ResourceController.execute(ResourceController.java:88)
at hudson.model.Executor.run(Executor.java:231)
Build step 'Publish Robot Framework test results' changed build result to FAILURE
Finished: FAILURE

It would be great to have an option to mark the build as failed or success whether or not the output_dir exists... So a check box in settings that says something along the lines of....
"Don't mark build as failed if output_dir doesn't exist.