Add require_submissions_enabled decorator to FileUploadViewSet Create (#22774)

* Added require_submissions_enabled decorator to FileUploadViewSet.create()

* fix test, linting

src/olympia/files/tests/test_views.py

@@ -121,6 +121,16 @@ class TestFileUploadViewSet(TestCase):
             )
         return response
 
+    def test_submissions_disabled(self):
+        self.create_flag('enable-submissions', note=':-(', everyone=False)
+        expected = {
+            'error': 'Add-on uploads are temporarily unavailable.',
+            'reason': ':-(',
+        }
+        response = self._create_post()
+        assert response.status_code == 503
+        assert response.json() == expected
+
     def test_not_authenticated(self):
         self.client.logout_api()
         response = self.client.get(

src/olympia/files/views.py

@@ -10,6 +10,7 @@ from rest_framework.viewsets import ReadOnlyModelViewSet
 
 import olympia.core.logger
 from olympia import amo
+from olympia.addons.decorators import require_submissions_enabled
 from olympia.amo.decorators import use_primary_db
 from olympia.amo.utils import HttpResponseXSendFile
 from olympia.api.authentication import (
@@ -72,6 +73,7 @@ class FileUploadViewSet(CreateModelMixin, ReadOnlyModelViewSet):
     def get_queryset(self):
         return super().get_queryset().filter(user=self.request.user)
 
+    @require_submissions_enabled
     def create(self, request):
         if 'upload' in request.FILES:
             filedata = request.FILES['upload']