bpo-36348: IMAP4.logout() doesn't ignore exc (GH-12411)

The imap.IMAP4.logout() method no longer ignores silently arbitrary
exceptions.

Changes:

* The IMAP4.logout() method now expects a "BYE" untagged response,
  rather than relying on _check_bye() which raises a self.abort()
  exception.
* IMAP4.__exit__() now does nothing if the client already logged out.
* Add more debug info if test_logout() tests fail.

1 files changed, 4 insertions, 4 deletions

diff --git a/Lib/test/test_imaplib.py b/Lib/test/test_imaplib.py
index aec36af..9305e47 100644
--- a/Lib/test/test_imaplib.py
+++ b/Lib/test/test_imaplib.py
@@ -470,8 +470,8 @@ class NewIMAPTestsMixin():
         self.assertEqual(typ, 'OK')
         self.assertEqual(data[0], b'LOGIN completed')
         typ, data = client.logout()
-        self.assertEqual(typ, 'BYE')
-        self.assertEqual(data[0], b'IMAP4ref1 Server logging out')
+        self.assertEqual(typ, 'BYE', (typ, data))
+        self.assertEqual(data[0], b'IMAP4ref1 Server logging out', (typ, data))
         self.assertEqual(client.state, 'LOGOUT')
 
     def test_lsub(self):
@@ -937,7 +937,7 @@ class RemoteIMAPTest(unittest.TestCase):
         with transient_internet(self.host):
             rs = self.server.logout()
             self.server = None
-            self.assertEqual(rs[0], 'BYE')
+            self.assertEqual(rs[0], 'BYE', rs)
 
 
 @unittest.skipUnless(ssl, "SSL not available")
@@ -995,7 +995,7 @@ class RemoteIMAP_SSLTest(RemoteIMAPTest):
         with transient_internet(self.host):
             _server = self.imap_class(self.host, self.port)
             rs = _server.logout()
-            self.assertEqual(rs[0], 'BYE')
+            self.assertEqual(rs[0], 'BYE', rs)
 
     def test_ssl_context_certfile_exclusive(self):
         with transient_internet(self.host):