Opens a unit test case's .out.compare file to examine the verbose comparison
        report across values.

def do_examine(self, arg):
        """Opens a unit test case's .out.compare file to examine the verbose comparison
        report across values.
        """
        #We use their default editor (if it has been set); otherwise we can't do much of
        #anything and issue a warning.
        from os import getenv, path, system
        testcase, output = arg.split()
        target = path.join(self.tests[self.active].stagedir, "tests", testcase, 
                           "{}.compare".format(output))
        if getenv("EDITOR") is not None:
            system("`$EDITOR {}`".format(target))
        else:
            msg.warn("$EDITOR not set in environment. Can't open {}".format(target))