From 1623cc202fa7cc6337d263e8407e8b5c4faf104d Mon Sep 17 00:00:00 2001
From: Florian Best <spaceone@users.noreply.github.com>
Date: Tue, 2 Jun 2026 22:42:04 +0200
Subject: [PATCH] gh-91099: fix[imaplib]: call Exception with string instance
 (GH-31823)

* bpo-46943: fix[imaplib]: call Exception with string instance

Adjust the behavior of 'login' to be similar to `authenticate()`,
where self.error is called with a str() instance.
(cherry picked from commit 29805f00a1b65163230d17584c30e2b955086abb)

Co-authored-by: Florian Best <spaceone@users.noreply.github.com>
Co-authored-by: Oleg Iarygin <oleg@arhadthedev.net>
---
 Lib/imaplib.py                                         |  2 +-
 Lib/test/test_imaplib.py                               | 10 ++++++++++
 .../2023-02-26-14-07-18.gh-issue-91099._QPbEL.rst      |  2 ++
 3 files changed, 13 insertions(+), 1 deletion(-)
 create mode 100644 Misc/NEWS.d/next/Library/2023-02-26-14-07-18.gh-issue-91099._QPbEL.rst

diff --git a/Lib/imaplib.py b/Lib/imaplib.py
index cbe129b3e7c2145..e84ffb2eecfbd38 100644
--- a/Lib/imaplib.py
+++ b/Lib/imaplib.py
@@ -706,7 +706,7 @@ def login(self, user, password):
         """
         typ, dat = self._simple_command('LOGIN', user, self._quote(password))
         if typ != 'OK':
-            raise self.error(dat[-1])
+            raise self.error(dat[-1].decode('UTF-8', 'replace'))
         self.state = 'AUTH'
         return typ, dat
 
diff --git a/Lib/test/test_imaplib.py b/Lib/test/test_imaplib.py
index a03d7b8bb2a42c1..f0b463949cad2f9 100644
--- a/Lib/test/test_imaplib.py
+++ b/Lib/test/test_imaplib.py
@@ -435,6 +435,16 @@ def cmd_AUTHENTICATE(self, tag, args):
                 r'\[AUTHENTICATIONFAILED\] invalid'):
             client.authenticate('MYAUTH', lambda x: b'fake')
 
+    def test_invalid_login(self):
+        class MyServer(SimpleIMAPHandler):
+            def cmd_LOGIN(self, tag, args):
+                self.server.logged = args[0]
+                self._send_tagged(tag, 'NO', '[LOGIN] failed')
+        client, _ = self._setup(MyServer)
+        with self.assertRaisesRegex(imaplib.IMAP4.error,
+                r'\[LOGIN\] failed'):
+            client.login('user', 'wrongpass')
+
     def test_valid_authentication_bytes(self):
         class MyServer(SimpleIMAPHandler):
             def cmd_AUTHENTICATE(self, tag, args):
diff --git a/Misc/NEWS.d/next/Library/2023-02-26-14-07-18.gh-issue-91099._QPbEL.rst b/Misc/NEWS.d/next/Library/2023-02-26-14-07-18.gh-issue-91099._QPbEL.rst
new file mode 100644
index 000000000000000..d886e8ac6032a4a
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2023-02-26-14-07-18.gh-issue-91099._QPbEL.rst
@@ -0,0 +1,2 @@
+:meth:`imaplib.IMAP4.login` now raises exceptions with :class:`str` instead of
+:class:`bytes`. Patch by Florian Best.