Django 1.10.1 + Wagtail 1.6.2 + django-debug-toolbar 1.5 = KeyError: 'wsgi.multiprocess'

I’m using Django 1.10.1 + Wagtail 1.6.2 + django-debug-toolbar 1.5. And when I click “Preview” button in admin interface, I get following error:

[ERROR] [django.request] [exception/handle_uncaught_exception] Internal Server Error: /cmspnl/pages/53/edit/preview/
Traceback (most recent call last):
  File "virtualenv\lib\site-packages\django\core\handlers\base.py", line 131, in get_response
    response = middleware_method(request, response)
  File "virtualenv\lib\site-packages\debug_toolbar\middleware.py", line 122, in process_response
    bits[-2] += toolbar.render_toolbar()
  File "virtualenv\lib\site-packages\debug_toolbar\toolbar.py", line 60, in render_toolbar
    if not self.should_render_panels():
  File "virtualenv\lib\site-packages\debug_toolbar\toolbar.py", line 81, in should_render_panels
    render_panels = self.request.META['wsgi.multiprocess']
KeyError: 'wsgi.multiprocess'

On other pages (which are also build in Wagtail, but accessed not via preview form) - all works fine. Also on Django 1.9 + Wagtail 1.5 + django-debug-toolbar 1.5 = all works fine too.

I think this issue is Wagtail-related.

I found this problem is related to code:

    def should_render_panels(self):
        render_panels = self.config['RENDER_PANELS']
        if render_panels is None:
            render_panels = self.request.META['wsgi.multiprocess']
        return render_panels

I’ve tried set RENDER_PANELS - but after this two Django-Toolbar panels are shown.

[mevinbabuc]

Currently this is the setting that works for me:

settings.py

    def show_toolbar(request):
        request.META["wsgi.multithread"] = True
        request.META["wsgi.multiprocess"] = True
        excluded_urls = ['/pages/preview/', '/pages/preview_loading/', '/edit/preview/']
        excluded = any(request.path.endswith(url) for url in excluded_urls)
        return DEBUG and not excluded

    DEBUG_TOOLBAR_CONFIG = {"SHOW_TOOLBAR_CALLBACK": show_toolbar, }

With this only one debug toolbar is shown in the page, as the other one is excluded.

[aaugustin]

I’m looking at this code: https://github.com/torchbox/wagtail/blob/3b4c24e0b59638fb695cfd0f2637b8e5bc595214/wagtail/wagtailcore/models.py#L1209-L1216

It should contain all values specified as mandatory by the WSGI spec: https://www.python.org/dev/peps/pep-3333/#environ-variables