Issue #28026: Raise ImportError when exec_module() exists but create_module() is missing.

Lib/importlib/_bootstrap.py

@@ -559,9 +559,8 @@ def module_from_spec(spec):
         # module creation should be used.
         module = spec.loader.create_module(spec)
     elif hasattr(spec.loader, 'exec_module'):
-        _warnings.warn('starting in Python 3.6, loaders defining exec_module() '
-                       'must also define create_module()',
-                       DeprecationWarning, stacklevel=2)
+        raise ImportError('loaders that define exec_module() '
+                          'must also define create_module()')
     if module is None:
         module = _new_module(spec.name)
     _init_module_attrs(spec, module)

Lib/test/test_importlib/test_util.py

@@ -47,14 +47,8 @@ class ModuleFromSpecTests:
             def exec_module(self, module):
                 pass
         spec = self.machinery.ModuleSpec('test', Loader())
-        with warnings.catch_warnings(record=True) as w:
-            warnings.simplefilter('always')
+        with self.assertRaises(ImportError):
             module = self.util.module_from_spec(spec)
-        self.assertEqual(1, len(w))
-        self.assertTrue(issubclass(w[0].category, DeprecationWarning))
-        self.assertIn('create_module', str(w[0].message))
-        self.assertIsInstance(module, types.ModuleType)
-        self.assertEqual(module.__name__, spec.name)
 
     def test_create_module_returns_None(self):
         class Loader(self.abc.Loader):

Misc/NEWS

@@ -6968,6 +6968,9 @@ Core and Builtins
 
 - Issue #19369: Optimized the usage of __length_hint__().
 
+- Issue #28026: Raise ImportError when exec_module() exists but
+  create_module() is missing.
+
 - Issue #18603: Ensure that PyOS_mystricmp and PyOS_mystrnicmp are in the
   Python executable and not removed by the linker's optimizer.