Add helpful information to base_layer.get_config NotImplementedError.

This makes it possible to identify which layer the problem originates from.

PiperOrigin-RevId: 295196040
Change-Id: I12ea152978a5a625b7c46f9c7713bec3206e3d87

tensorflow/python/keras/engine/base_layer.py

@@ -523,8 +523,9 @@ class Layer(module.Module, version_utils.LayerVersionSelector):
     # Check that either the only argument in the `__init__` is  `self`,
     # or that `get_config` has been overridden:
     if len(extra_args) > 1 and hasattr(self.get_config, '_is_default'):
-      raise NotImplementedError('Layers with arguments in `__init__` must '
-                                'override `get_config`.')
+      raise NotImplementedError('Layer %s has arguments in `__init__` and '
+                                'therefore must override `get_config`.' %
+                                self.__class__.__name__)
     return config
 
   @classmethod

tensorflow/python/keras/engine/base_layer_test.py

@@ -535,7 +535,7 @@ class BaseLayerTest(keras_parameterized.TestCase):
 
     # `__init__` includes kwargs but `get_config` is not overridden, so
     # an error should be thrown:
-    with self.assertRaises(NotImplementedError):
+    with self.assertRaisesRegexp(NotImplementedError, 'Layer MyLayer has'):
       MyLayer('custom').get_config()
 
     class MyLayerNew(keras.layers.Layer):