diff --git a/apps/participation/management/commands/setup_third_phase.py b/apps/participation/management/commands/setup_third_phase.py
index cab873e..3034354 100644
--- a/apps/participation/management/commands/setup_third_phase.py
+++ b/apps/participation/management/commands/setup_third_phase.py
@@ -1,6 +1,5 @@
-from django.core.management import BaseCommand
-
 from corres2math.matrix import Matrix, RoomVisibility
+from django.core.management import BaseCommand
 from participation.models import Participation
 
 
diff --git a/apps/participation/models.py b/apps/participation/models.py
index 0d5e5fb..746550f 100644
--- a/apps/participation/models.py
+++ b/apps/participation/models.py
@@ -245,6 +245,9 @@ class Question(models.Model):
         verbose_name=_("question"),
     )
 
+    def __str__(self):
+        return self.question
+
 
 class Phase(models.Model):
     """
diff --git a/apps/participation/views.py b/apps/participation/views.py
index 6e6970b..ccf62b4 100644
--- a/apps/participation/views.py
+++ b/apps/participation/views.py
@@ -449,7 +449,6 @@ class DeleteQuestionView(LoginRequiredMixin, DeleteView):
         return reverse_lazy("participation:participation_detail", args=(self.object.participation.pk,))
 
 
-
 class UploadVideoView(LoginRequiredMixin, UpdateView):
     """
     Upload a solution video for a team.
diff --git a/apps/registration/signals.py b/apps/registration/signals.py
index 3a4c7a3..ff89f65 100644
--- a/apps/registration/signals.py
+++ b/apps/registration/signals.py
@@ -1,7 +1,7 @@
 from corres2math.lists import get_sympa_client
+from corres2math.matrix import Matrix
 from django.contrib.auth.models import User
 
-from corres2math.matrix import Matrix
 from .models import AdminRegistration, Registration