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Co-authored-by: Victor Stinner <vstinner@python.org>

Author: StanFromIreland

Lib/test/test_import/test_lazy_imports.py

@@ -393,14 +393,14 @@ def test_dunder_lazy_import_used(self):
         import test.test_import.data.lazy_imports.dunder_lazy_import_used
         self.assertIn("test.test_import.data.lazy_imports.basic2", sys.modules)
 
-    def test_dunder_lazy_import_non_string_name(self):
-        """__lazy_import__ should reject non-string name arguments."""
-        with self.assertRaises(TypeError):
-            __lazy_import__(b"")
-        with self.assertRaises(TypeError):
-            __lazy_import__(123)
-        with self.assertRaises(TypeError):
-            __lazy_import__(None)
+    def test_dunder_lazy_import_invalid_arguments(self):
+        """__lazy_import__ should reject invalid arguments."""
+        for invalid_name in (b"", 123, None):
+            with self.assertRaises(TypeError):
+                __lazy_import__(invalid_name)
+
+        with self.assertRaises(ValueError):
+            __lazy_import__("sys", level=-1)
 
     def test_dunder_lazy_import_builtins(self):
         """__lazy_import__ should use module's __builtins__ for __import__."""

Python/import.c

@@ -4473,8 +4473,8 @@ _PyImport_LazyImportModuleLevelObject(PyThreadState *tstate,
         return NULL;
     }
     if (!PyUnicode_Check(name)) {
-        _PyErr_SetString(tstate, PyExc_TypeError,
-                         "module name must be a string");
+        _PyErr_Format(tstate, PyExc_TypeError,
+                      "module name must be a string, got %T", name);
         return NULL;
     }
     if (level < 0) {