Fix serving media-URLs for development (#4355)

src/pretix/urls.py

@@ -33,6 +33,7 @@
 # License for the specific language governing permissions and limitations under the License.
 
 from django.conf import settings
+from django.conf.urls.static import static
 from django.urls import include, re_path
 from django.views.generic import RedirectView
 
@@ -68,6 +69,7 @@ control_patterns = [
 
 debug_patterns = []
 if settings.DEBUG:
+    base_patterns += static(settings.MEDIA_URL, document_root=settings.MEDIA_ROOT)
     try:
         import debug_toolbar