Refs #26421 -- Refactored Apps.lazy_model_operation() for better checks and tests

1 files changed, 15 insertions, 9 deletions

diff --git a/django/db/models/utils.py b/django/db/models/utils.py
index f696e30ce2..cda96277a6 100644
--- a/django/db/models/utils.py
+++ b/django/db/models/utils.py
@@ -7,12 +7,18 @@ def make_model_tuple(model):
     corresponding ("app_label", "modelname") tuple. If a tuple is passed in,
     it's assumed to be a valid model tuple already and returned unchanged.
     """
-    if isinstance(model, tuple):
-        model_tuple = model
-    elif isinstance(model, six.string_types):
-        app_label, model_name = model.split(".")
-        model_tuple = app_label, model_name.lower()
-    else:
-        model_tuple = model._meta.app_label, model._meta.model_name
-    assert len(model_tuple) == 2, "Invalid model representation: %s" % model
-    return model_tuple
+    try:
+        if isinstance(model, tuple):
+            model_tuple = model
+        elif isinstance(model, six.string_types):
+            app_label, model_name = model.split(".")
+            model_tuple = app_label, model_name.lower()
+        else:
+            model_tuple = model._meta.app_label, model._meta.model_name
+        assert len(model_tuple) == 2
+        return model_tuple
+    except (ValueError, AssertionError):
+        raise ValueError(
+            "Invalid model reference '%s'. String model references "
+            "must be of the form 'app_label.ModelName'." % model
+        )