Validate a debugger plugin, ensuring it is a debugger plugin and has
        the necessary fields present.

        `plugin` is a subclass of scruffy's Plugin class.

def valid_debugger_plugin(self, plugin):
        """
        Validate a debugger plugin, ensuring it is a debugger plugin and has
        the necessary fields present.

        `plugin` is a subclass of scruffy's Plugin class.
        """
        if (issubclass(plugin, DebuggerAdaptorPlugin) and
            hasattr(plugin, 'plugin_type')      and plugin.plugin_type == 'debugger' and
            hasattr(plugin, 'host')             and plugin.host != None):
            return True
        return False