Hide import of DocumentSerializer, causes migration errors

mayan/apps/folders/api_views.py

@@ -8,7 +8,6 @@ from rest_framework import generics
 from acls.models import AccessEntry
 from documents.models import Document
 from documents.permissions import PERMISSION_DOCUMENT_VIEW
-from documents.serializers import DocumentSerializer
 from permissions.models import Permission
 from rest_api.filters import MayanObjectPermissionsFilter
 from rest_api.permissions import MayanPermission
@@ -57,7 +56,10 @@ class APIFolderDocumentListView(generics.ListAPIView):
 
     filter_backends = (MayanObjectPermissionsFilter,)
     mayan_object_permissions = {'GET': [PERMISSION_DOCUMENT_VIEW]}
-    serializer_class = FolderSerializer
+
+    def get_serializer_class(self):
+        from documents.serializers import DocumentSerializer
+        return DocumentSerializer
 
     def get_queryset(self):
         folder = get_object_or_404(Folder, pk=self.kwargs['pk'])