def _get_plugin_module_paths(self, plugin_dir):
        ''' Return a list of every module in `plugin_dir`. '''
        filepaths = [
            fp for fp in glob.glob('{}/**/*.py'.format(plugin_dir), recursive=True)
            if not fp.endswith('__init__.py')
        ]
        rel_paths = [re.sub(plugin_dir.rstrip('/') + '/', '', fp) for fp in filepaths]
        module_paths = [rp.replace('/', '.').replace('.py', '') for rp in rel_paths]

        return module_paths
Return a list of every module in `plugin_dir`.