def err(self, output, newline=True):
        click.echo(output, nl=newline, err=True)
values appended to the OptionVarList with this method will be added to the Maya optionVar at the key denoted by self.key.
dataset/ETHPy150Open softlayer/softlayer-python/SoftLayer/CLI/environment.py/Environment.err--crossover with--dataset/ETHPy150Open CountZer0/PipelineConstructionSet/python/maya/site-packages/pymel-1.0.5/extras/completion/py/pymel/core/language.py/OptionVarList.appendVar