bpo-30329: Catch Windows error 10022 on shutdown() (#1538)

Catch the Windows socket WSAEINVAL error (code 10022) in imaplib and
poplib on shutdown(SHUT_RDWR): An invalid operation was attempted

This error occurs sometimes on SSL connections.

1 files changed, 6 insertions, 3 deletions

diff --git a/Lib/poplib.py b/Lib/poplib.py
index cae6950eb6..6bcfa5cfeb 100644
--- a/Lib/poplib.py
+++ b/Lib/poplib.py
@@ -288,9 +288,12 @@ class POP3:
             if sock is not None:
                 try:
                     sock.shutdown(socket.SHUT_RDWR)
-                except OSError as e:
-                    # The server might already have closed the connection
-                    if e.errno != errno.ENOTCONN:
+                except OSError as exc:
+                    # The server might already have closed the connection.
+                    # On Windows, this may result in WSAEINVAL (error 10022):
+                    # An invalid operation was attempted.
+                    if (exc.errno != errno.ENOTCONN
+                       and getattr(exc, 'winerror', 0) != 10022):
                         raise
                 finally:
                     sock.close()