private void showErrorMessage(String message) {
		SystemUtilities.runSwingLater(() -> Msg.showError(getClass(),
			plugin.getTool().getToolFrame(), "Can't Perform Diff", message));
	}
This is the method TaskMonitor called to do the work.

@param monitor The TaskMonitor that will monitor the executing Task.  Will be null if
		  this task declared that it does not use a TaskMonitor
Ghidra/Features/ProgramDiff/src/main/java/ghidra/app/plugin/core/diff/CreateDiffTask.java