bpo-43510: PEP 597: Accept `encoding="locale"` in binary mode (GH-25103)

It make `encoding="locale"` usable everywhere `encoding=None` is
allowed.

1 files changed, 1 insertions, 1 deletions

diff --git a/Lib/_pyio.py b/Lib/_pyio.py
index 0f182d4240..ba0b0a29b5 100644
--- a/Lib/_pyio.py
+++ b/Lib/_pyio.py
@@ -221,7 +221,7 @@ def open(file, mode="r", buffering=-1, encoding=None, errors=None,
         raise ValueError("can't have read/write/append mode at once")
     if not (creating or reading or writing or appending):
         raise ValueError("must have exactly one of read/write/append mode")
-    if binary and encoding is not None:
+    if binary and encoding is not None and encoding != "locale":
         raise ValueError("binary mode doesn't take an encoding argument")
     if binary and errors is not None:
         raise ValueError("binary mode doesn't take an errors argument")