diff --git a/cotisations/migrations/0051_auto_20201228_1636.py b/cotisations/migrations/0051_auto_20201228_1636.py
index 031ccf63..572c9634 100644
--- a/cotisations/migrations/0051_auto_20201228_1636.py
+++ b/cotisations/migrations/0051_auto_20201228_1636.py
@@ -8,38 +8,52 @@ from django.db import migrations, models
 class Migration(migrations.Migration):
 
     dependencies = [
-        ('cotisations', '0050_auto_20201102_2342'),
+        ("cotisations", "0050_auto_20201102_2342"),
     ]
 
     operations = [
         migrations.AlterField(
-            model_name='article',
-            name='duration_connection',
-            field=models.PositiveIntegerField(verbose_name='duration of the connection (in months)'),
+            model_name="article",
+            name="duration_connection",
+            field=models.PositiveIntegerField(
+                verbose_name="duration of the connection (in months)"
+            ),
         ),
         migrations.AlterField(
-            model_name='article',
-            name='duration_days_connection',
-            field=models.PositiveIntegerField(verbose_name='duration of the connection (in days, will be added to duration in months)'),
+            model_name="article",
+            name="duration_days_connection",
+            field=models.PositiveIntegerField(
+                verbose_name="duration of the connection (in days, will be added to duration in months)"
+            ),
         ),
         migrations.AlterField(
-            model_name='article',
-            name='duration_days_membership',
-            field=models.PositiveIntegerField(verbose_name='duration of the membership (in days, will be added to duration in months)'),
+            model_name="article",
+            name="duration_days_membership",
+            field=models.PositiveIntegerField(
+                verbose_name="duration of the membership (in days, will be added to duration in months)"
+            ),
         ),
         migrations.AlterField(
-            model_name='article',
-            name='duration_membership',
-            field=models.PositiveIntegerField(verbose_name='duration of the membership (in months)'),
+            model_name="article",
+            name="duration_membership",
+            field=models.PositiveIntegerField(
+                verbose_name="duration of the membership (in months)"
+            ),
         ),
         migrations.AlterField(
-            model_name='vente',
-            name='duration_days_connection',
-            field=models.PositiveIntegerField(default=0, verbose_name='duration of the connection (in days, will be added to duration in months)'),
+            model_name="vente",
+            name="duration_days_connection",
+            field=models.PositiveIntegerField(
+                default=0,
+                verbose_name="duration of the connection (in days, will be added to duration in months)",
+            ),
         ),
         migrations.AlterField(
-            model_name='vente',
-            name='duration_days_membership',
-            field=models.PositiveIntegerField(default=0, verbose_name='duration of the membership (in days, will be added to duration in months)'),
+            model_name="vente",
+            name="duration_days_membership",
+            field=models.PositiveIntegerField(
+                default=0,
+                verbose_name="duration of the membership (in days, will be added to duration in months)",
+            ),
         ),
     ]
diff --git a/cotisations/models.py b/cotisations/models.py
index 328a2657..5dc18e4f 100644
--- a/cotisations/models.py
+++ b/cotisations/models.py
@@ -98,7 +98,7 @@ class BaseInvoice(RevMixin, AclMixin, FieldPermissionModelMixin, models.Model):
 
     def name_detailed(self):
         """
-        Return: 
+        Return:
          - a list of strings with the name of all article in the invoice
         and their quantity.
         """
@@ -248,8 +248,8 @@ class Facture(BaseInvoice):
 
     @staticmethod
     def can_change_control(user_request, *_args, **_kwargs):
-        """ Returns True if the user can change the 'controlled' status of
-        this invoice """
+        """Returns True if the user can change the 'controlled' status of
+        this invoice"""
         can = user_request.has_perm("cotisations.change_facture_control")
         return (
             can,
@@ -293,8 +293,7 @@ class Facture(BaseInvoice):
         """Returns every subscription associated with this invoice."""
         return Cotisation.objects.filter(
             vente__in=self.vente_set.filter(
-                ~(Q(duration_membership=0)) |\
-                ~(Q(duration_days_membership=0))
+                ~(Q(duration_membership=0)) | ~(Q(duration_days_membership=0))
             )
         )
 
@@ -454,7 +453,7 @@ class Vente(RevMixin, AclMixin, models.Model):
     number = models.IntegerField(
         validators=[MinValueValidator(1)], verbose_name=_("amount")
     )
-    # TODO : change this field for a ForeinKey to Article 
+    # TODO : change this field for a ForeinKey to Article
     # Note: With a foreign key, modifing an Article modifis the Purchase, wich is bad.
     # To use a foreign key, you need to make Article read only
     name = models.CharField(max_length=255, verbose_name=_("article"))
@@ -467,14 +466,18 @@ class Vente(RevMixin, AclMixin, models.Model):
     )
     duration_days_connection = models.PositiveIntegerField(
         default=0,
-        verbose_name=_("duration of the connection (in days, will be added to duration in months)"),
+        verbose_name=_(
+            "duration of the connection (in days, will be added to duration in months)"
+        ),
     )
     duration_membership = models.PositiveIntegerField(
         default=0, verbose_name=_("duration of the membership (in months)")
     )
     duration_days_membership = models.PositiveIntegerField(
         default=0,
-        verbose_name=_("duration of the membership (in days, will be added to duration in months)"),
+        verbose_name=_(
+            "duration of the membership (in days, will be added to duration in months)"
+        ),
     )
 
     class Meta:
@@ -511,7 +514,7 @@ class Vente(RevMixin, AclMixin, models.Model):
 
     def create_cotis(self, date_start_con=False, date_start_memb=False):
         """
-        Creates a cotisation without initializing the dates (start and end ar set to self.facture.facture.date) 
+        Creates a cotisation without initializing the dates (start and end ar set to self.facture.facture.date)
         and without saving it. You should use Facture.reorder_purchases to set the right dates.
         """
         try:
@@ -629,12 +632,14 @@ class Vente(RevMixin, AclMixin, models.Model):
         return str(self.name) + " " + str(self.facture)
 
     def test_membership_or_connection(self):
-        """ Test if the purchase include membership or connecton
-        """
-        return self.duration_membership or \
-               self.duration_days_membership or \
-               self.duration_connection or \
-               self.duration_days_connection
+        """Test if the purchase include membership or connecton"""
+        return (
+            self.duration_membership
+            or self.duration_days_membership
+            or self.duration_connection
+            or self.duration_days_connection
+        )
+
 
 # TODO : change vente to purchase
 @receiver(post_save, sender=Vente)
@@ -705,13 +710,17 @@ class Article(RevMixin, AclMixin, models.Model):
         verbose_name=_("duration of the membership (in months)")
     )
     duration_days_membership = models.PositiveIntegerField(
-        verbose_name=_("duration of the membership (in days, will be added to duration in months)"),
+        verbose_name=_(
+            "duration of the membership (in days, will be added to duration in months)"
+        ),
     )
     duration_connection = models.PositiveIntegerField(
         verbose_name=_("duration of the connection (in months)")
     )
     duration_days_connection = models.PositiveIntegerField(
-        verbose_name=_("duration of the connection (in days, will be added to duration in months)"),
+        verbose_name=_(
+            "duration of the connection (in days, will be added to duration in months)"
+        ),
     )
 
     need_membership = models.BooleanField(
@@ -787,8 +796,8 @@ class Article(RevMixin, AclMixin, models.Model):
         if target_user is not None and not target_user.is_adherent():
             objects_pool = objects_pool.filter(
                 Q(duration_membership__gt=0)
-                |Q(duration_days_membership__gt=0)
-                |Q(need_membership=False)
+                | Q(duration_days_membership__gt=0)
+                | Q(need_membership=False)
             )
         if user.has_perm("cotisations.buy_every_article"):
             return objects_pool
@@ -878,7 +887,9 @@ class Paiement(RevMixin, AclMixin, models.Model):
 
         # In case a cotisation was bought, inform the user, the
         # cotisation time has been extended too
-        if any(sell.test_membership_or_connection() for sell in invoice.vente_set.all()):
+        if any(
+            sell.test_membership_or_connection() for sell in invoice.vente_set.all()
+        ):
             messages.success(
                 request,
                 _(
@@ -950,9 +961,13 @@ class Cotisation(RevMixin, AclMixin, models.Model):
     vente = models.OneToOneField(
         "Vente", on_delete=models.CASCADE, null=True, verbose_name=_("purchase")
     )
-    date_start_con = models.DateTimeField(verbose_name=_("start date for the connection"))
+    date_start_con = models.DateTimeField(
+        verbose_name=_("start date for the connection")
+    )
     date_end_con = models.DateTimeField(verbose_name=_("end date for the connection"))
-    date_start_memb = models.DateTimeField(verbose_name=_("start date for the membership"))
+    date_start_memb = models.DateTimeField(
+        verbose_name=_("start date for the membership")
+    )
     date_end_memb = models.DateTimeField(verbose_name=_("end date for the membership"))
 
     class Meta: