remove codecs.open from error message

Author: methane

Lib/_pyio.py

@@ -2056,8 +2056,7 @@ def __init__(self, buffer, encoding=None, errors=None, newline=None,
             raise ValueError("invalid encoding: %r" % encoding)
 
         if not codecs.lookup(encoding)._is_text_encoding:
-            msg = ("%r is not a text encoding; "
-                   "use codecs.open() to handle arbitrary codecs")
+            msg = "%r is not a text encoding"
             raise LookupError(msg % encoding)
 
         if errors is None:

Modules/_io/textio.c

@@ -1185,7 +1185,7 @@ _io_TextIOWrapper___init___impl(textio *self, PyObject *buffer,
     }
 
     /* Check we have been asked for a real text encoding */
-    codec_info = _PyCodec_LookupTextEncoding(encoding, "codecs.open()");
+    codec_info = _PyCodec_LookupTextEncoding(encoding, NULL);
     if (codec_info == NULL) {
         Py_CLEAR(self->encoding);
         goto error;
@@ -1324,8 +1324,7 @@ textiowrapper_change_encoding(textio *self, PyObject *encoding,
     }
 
     // Create new encoder & decoder
-    PyObject *codec_info = _PyCodec_LookupTextEncoding(
-        c_encoding, "codecs.open()");
+    PyObject *codec_info = _PyCodec_LookupTextEncoding(c_encoding, NULL);
     if (codec_info == NULL) {
         Py_DECREF(encoding);
         Py_DECREF(errors);

Python/codecs.c

@@ -540,11 +540,19 @@ PyObject * _PyCodec_LookupTextEncoding(const char *encoding,
             Py_DECREF(attr);
             if (is_text_codec <= 0) {
                 Py_DECREF(codec);
-                if (!is_text_codec)
-                    PyErr_Format(PyExc_LookupError,
-                                 "'%.400s' is not a text encoding; "
-                                 "use %s to handle arbitrary codecs",
-                                 encoding, alternate_command);
+                if (!is_text_codec) {
+                    if (alternate_command != NULL) {
+                        PyErr_Format(PyExc_LookupError,
+                                     "'%.400s' is not a text encoding; "
+                                     "use %s to handle arbitrary codecs",
+                                     encoding, alternate_command);
+                    }
+                    else {
+                        PyErr_Format(PyExc_LookupError,
+                                     "'%.400s' is not a text encoding",
+                                     encoding);
+                    }
+                }
                 return NULL;
             }
         }