Issue #20404: reject non-text encodings early in TextIOWrapper.
diff --git a/Lib/_pyio.py b/Lib/_pyio.py
index 9a2a1aa..a0c4b25 100644
--- a/Lib/_pyio.py
+++ b/Lib/_pyio.py
@@ -1495,6 +1495,11 @@
if not isinstance(encoding, str):
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")
+ raise LookupError(msg % encoding)
+
if errors is None:
errors = "strict"
else: