'register a command line option.
:opts: option names, can be short or long options.
:attrs: same attributes which the ``add_option()`` function of the
`argparse library
<http://docs.python.org/2/library/argparse.html>`_
accepts.
After command line parsing options are available on the pytest config
object via ``config.option.NAME`` where ``NAME`` is usually set
by passing a ``dest`` attribute, for example
``addoption("--long", dest="NAME", ...)``.'

def addoption(self, *opts, **attrs):

    self._anonymous.addoption(*opts, **attrs)
