Allow OPTIONS to retrieve PUT field metadata on empty objects

This allows OPTIONS to return the PUT endpoint's object serializer metadata when the object hasn't been created yet.

rest_framework/generics.py

@@ -356,8 +356,13 @@ class GenericAPIView(views.APIView):
                 self.check_permissions(cloned_request)
                 # Test object permissions
                 if method == 'PUT':
-                    self.get_object()
-            except (exceptions.APIException, PermissionDenied, Http404):
+                    try:
+                        self.get_object()
+                    except Http404:
+                        # Http404 should be acceptable and the serializer
+                        # metadata should be populated.
+                        pass
+            except (exceptions.APIException, PermissionDenied):
                 pass
             else:
                 # If user has appropriate permissions for the view, include