Upgrade to Django 3.2 (#2056)

src/pretix/api/serializers/cart.py

@@ -19,6 +19,7 @@
 # You should have received a copy of the GNU Affero General Public License along with this program.  If not, see
 # <https://www.gnu.org/licenses/>.
 #
+import os
 from datetime import timedelta
 
 from django.core.files import File
@@ -125,9 +126,10 @@ class CartPositionCreateSerializer(I18nAwareModelSerializer):
             if isinstance(answ_data['answer'], File):
                 an = answ_data.pop('answer')
                 answ = cp.answers.create(**answ_data, answer='')
-                answ.file.save(an.name, an, save=False)
+                answ.file.save(os.path.basename(an.name), an, save=False)
                 answ.answer = 'file://' + answ.file.name
                 answ.save()
+                an.close()
             else:
                 answ = cp.answers.create(**answ_data)
                 answ.options.add(*options)