Improve error message when model name not registered

Summary: This assertion masks the missing model name from the error message, which makes it hard to debug. This diff adds the name into the error.

Differential Revision: D39513464

fbshipit-source-id: 41ba0651832cd72f5545551c24f9faec5ff2bc57

Author: Andrew Ho

classy_vision/models/__init__.py

@@ -78,7 +78,7 @@ def build_model(config):
     "foo": "bar"}` will find a class that was registered as "my_model"
     (see :func:`register_model`) and call .from_config on it."""
 
-    assert config["name"] in MODEL_REGISTRY, "unknown model"
+    assert config["name"] in MODEL_REGISTRY, f"unknown model: {config['name']}"
     model = MODEL_REGISTRY[config["name"]].from_config(config)
     if "heads" in config:
         heads = defaultdict(list)

test/models_classy_model_test.py

@@ -83,6 +83,21 @@ def get_model_config(self, use_head):
             ]
         return config
 
+    def test_model_bad_name(self):
+        config = self.get_model_config(use_head=True)
+        test_bad_name = "__test_bad_name__"
+        config["name"] = test_bad_name
+
+        try:
+            _ = build_model(config)
+        except AssertionError as e:
+            self.assertTrue(
+                test_bad_name in str(e),
+                f"expected {test_bad_name} in error message, got {str(e)}",
+            )
+            return
+        self.assertTrue(False, "expected an AssertionError to be thrown")
+
     def test_from_checkpoint(self):
         config = get_test_task_config()
         for use_head in [True, False]: