django调试工具栏抛出配置不正确的异常

Question

我安装了django 1.9和django调试工具栏==1.3.0。这是我的设置.py内容

# debug_toolbar settings
if DEBUG:
    INTERNAL_IPS = ('127.0.0.1',)
    MIDDLEWARE_CLASSES += (
        'debug_toolbar.middleware.DebugToolbarMiddleware',
    )
    INSTALLED_APPS += (
        'debug_toolbar',
    )
    DEBUG_TOOLBAR_PANELS = [
        'debug_toolbar.panels.versions.VersionsPanel',
        'debug_toolbar.panels.timer.TimerPanel',
        'debug_toolbar.panels.settings.SettingsPanel',
        'debug_toolbar.panels.headers.HeadersPanel',
        'debug_toolbar.panels.request.RequestPanel',
        'debug_toolbar.panels.sql.SQLPanel',
        'debug_toolbar.panels.staticfiles.StaticFilesPanel',
        'debug_toolbar.panels.templates.TemplatesPanel',
        'debug_toolbar.panels.cache.CachePanel',
        'debug_toolbar.panels.signals.SignalsPanel',
        'debug_toolbar.panels.logging.LoggingPanel',
        'debug_toolbar.panels.redirects.RedirectsPanel',
    ]
    DEBUG_TOOLBAR_CONFIG = {
        'INTERCEPT_REDIRECTS': False,
    }

我已经验证了DEBUG设置为True。当运行服务器时，我得到以下错误-

django.core.exceptions.ImproperlyConfigured: Error importing debug panel debug_toolbar.panels.versions: "cannot import name linebreak_iter"

整个堆栈可以在这里找到-https://gist.github.com/anonymous/7a48e7c24d530118e5dfc0a75b982be2

出了什么问题？TIA。