Setup mailman3 server

We want to migrate to mailman3 as mailman2 is basically unmaintained and requires Python 2 which is EOL.

Because the mailman and mailman3 packages conflict and we don't want to perform a big bang migration, mailman3 must be deployed on a separate server. mailman-web (mailman3's web interface) hasn't been packaged yet, so for now we are using my homebrewed PKGBUILD.

[1] https://gist.github.com/klausenbusk/5982063f95c503754a51ed2fefb8915e

Ref #59 (closed)

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Migrated lists:

• arch-announce
• arch-devops-private
• arch-events
• arch-wiki-admins

roles/mailman3/templates/urls.py.j2

@@ -17,19 +17,19 @@
 # Postorius.  If not, see <http://www.gnu.org/licenses/>.
 
 
-from django.conf.urls import include, url
+from django.urls import include, path
 from django.contrib import admin
 from django.urls import reverse_lazy
 from django.views.generic import RedirectView
 
 urlpatterns = [
-    url(r'^$', RedirectView.as_view(
+    path('', RedirectView.as_view(
         url=reverse_lazy('list_index'),
         permanent=True)),
-    url(r'^mailman3/', include('postorius.urls')),
-    url(r'^archives/', include('hyperkitty.urls')),
-    url(r'', include('django_mailman3.urls')),
-    url(r'^accounts/', include('allauth.urls')),
+    path('mailman3/', include('postorius.urls')),
+    path('archives/', include('hyperkitty.urls')),
+    path('', include('django_mailman3.urls')),
+    path('accounts/', include('allauth.urls')),
     # Django admin
-    url(r'^admin3/', admin.site.urls),
+    path('admin3/', admin.site.urls),
 ]