Oh, AppVeyor failed on my PR:

test_linetoolong (test.test_imaplib.ThreadedNetworkedTestsSSL) ...
creating server
server created
ADDR = ('127.0.0.1', 0)
CLASS = test.test_imaplib.SecureTCPServer
HDLR = test.test_imaplib.TooLongHandler
server running
waiting for server
done
ERROR

(...)

ERROR: test_linetoolong (test.test_imaplib.ThreadedNetworkedTestsSSL)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:\projects\cpython\lib\test\test_imaplib.py", line 176, in test_linetoolong
    self.imap_class, *server.server_address)
  File "C:\projects\cpython\lib\unittest\case.py", line 473, in assertRaises
    callableObj(*args, **kwargs)
  File "C:\projects\cpython\lib\imaplib.py", line 1169, in __init__
    IMAP4.__init__(self, host, port)
  File "C:\projects\cpython\lib\imaplib.py", line 203, in __init__
    typ, dat = self.capability()
  File "C:\projects\cpython\lib\imaplib.py", line 377, in capability
    typ, dat = self._simple_command(name)
  File "C:\projects\cpython\lib\imaplib.py", line 1091, in _simple_command
    return self._command_complete(name, self._command(name, *args))
  File "C:\projects\cpython\lib\imaplib.py", line 913, in _command_complete
    typ, data = self._get_tagged_response(tag)
  File "C:\projects\cpython\lib\imaplib.py", line 1020, in _get_tagged_response
    self._get_response()
  File "C:\projects\cpython\lib\imaplib.py", line 932, in _get_response
    resp = self._get_line()
  File "C:\projects\cpython\lib\imaplib.py", line 1030, in _get_line
    line = self.readline()
  File "C:\projects\cpython\lib\imaplib.py", line 1192, in readline
    return self.file.readline()
  File "C:\projects\cpython\lib\socket.py", line 451, in readline
    data = self._sock.recv(self._rbufsize)
  File "C:\projects\cpython\lib\ssl.py", line 772, in recv
    return self.read(buflen)
  File "C:\projects\cpython\lib\ssl.py", line 659, in read
    v = self._sslobj.read(len)
error: [Errno 10053] An established connection was aborted by the software in your host machine