[Backport] Fix error when delete projects directly in the admin panel list

taiga/projects/admin.py

@@ -176,8 +176,10 @@ class ProjectAdmin(admin.ModelAdmin):
     ## Actions
     actions = [
         "make_public",
-        "make_private"
+        "make_private",
+        "delete_selected"
     ]
+
     @transaction.atomic
     def make_public(self, request, queryset):
         total_updates = 0
@@ -210,6 +212,36 @@ class ProjectAdmin(admin.ModelAdmin):
         self.message_user(request, _("{count} successfully made private.").format(count=total_updates))
     make_private.short_description = _("Make private")
 
+    def delete_selected(self, request, queryset):
+        # NOTE: This must be equal to taiga.projects.models.Project.delete_related_content
+        from taiga.events.apps import (connect_events_signals,
+                                       disconnect_events_signals)
+        from taiga.projects.tasks.apps import (connect_all_tasks_signals,
+                                               disconnect_all_tasks_signals)
+        from taiga.projects.userstories.apps import (connect_all_userstories_signals,
+                                                     disconnect_all_userstories_signals)
+        from taiga.projects.issues.apps import (connect_all_issues_signals,
+                                                disconnect_all_issues_signals)
+        from taiga.projects.apps import (connect_memberships_signals,
+                                         disconnect_memberships_signals)
+
+        disconnect_events_signals()
+        disconnect_all_issues_signals()
+        disconnect_all_tasks_signals()
+        disconnect_all_userstories_signals()
+        disconnect_memberships_signals()
+
+        r =  admin.actions.delete_selected(self, request, queryset)
+
+        connect_events_signals()
+        connect_all_issues_signals()
+        connect_all_tasks_signals()
+        connect_all_userstories_signals()
+        connect_memberships_signals()
+
+        return r
+    delete_selected.short_description = _("Delete selected %(verbose_name_plural)s")
+
 
 # User Stories common admins
 class PointsAdmin(admin.ModelAdmin):

taiga/projects/models.py

@@ -467,6 +467,7 @@ class Project(ProjectDefaults, TaggedMixin, models.Model):
         set_notify_policy_level_to_ignore(notify_policy)
 
     def delete_related_content(self):
+        # NOTE: Remember to update code in taiga.projects.admin.ProjectAdmin.delete_selected
         from taiga.events.apps import (connect_events_signals,
                                        disconnect_events_signals)
         from taiga.projects.tasks.apps import (connect_all_tasks_signals,