Outputs to stdout the list of checks that glerbl knows about. The
    format of the list is::

        module_name [list of hooks]

           docstring

    The identifier ``module_name`` is the name of the module
    implementing the check. This name is how you'd refer to the check
    in your ``glerbl.conf.py`` file. The ``[list of hooks]`` is a list
    of hook name to which this check can be applied. The ``docstring``
    is a description of what the hook does.

def _listchecks(_):
    """
    Outputs to stdout the list of checks that glerbl knows about. The
    format of the list is::

        module_name [list of hooks]

           docstring

    The identifier ``module_name`` is the name of the module
    implementing the check. This name is how you'd refer to the check
    in your ``glerbl.conf.py`` file. The ``[list of hooks]`` is a list
    of hook name to which this check can be applied. The ``docstring``
    is a description of what the hook does.

    """
    import glerbl.check
    package = glerbl.check
    for _, modname, _ in pkgutil.walk_packages(path=package.__path__):
        mod = importlib.import_module(package.__name__+ '.' + modname)
        print(modname, mod.Check.hooks)
        print(mod.Check.__doc__)