make import_methods fail if djang-rest-framework is too old
diff --git a/xos/api/import_methods.py b/xos/api/import_methods.py
index 13502d4..2a6ca57 100644
--- a/xos/api/import_methods.py
+++ b/xos/api/import_methods.py
@@ -5,6 +5,11 @@
 import inspect
 import importlib
 
+try:
+    from rest_framework.serializers import DictField
+except:
+    raise Exception("Failed check for django-rest-framework >= 3.3.3")
+
 urlpatterns = []
 
 def import_module_from_filename(dirname, fn):