Hang up reading Yandex mail box listing.

Hi, guys.

I'm using getmail on my Archlinux machine. Latest version -- 5.13. I
have a few mail boxes configured: Gmail and Yandex.Mail [1]. Gmail
works fine but Yandex sometime causes Getmail hang up. It happens
pretty often: every 1-3 days (getmail runs every 3 minutes by systemd
timer). During my experiments I've found the place where mail box
retrieval process stops.

Python process keeps running:
$ ps aux | grep getmail
24207 ?        S      0:08 python2 -u /bin/getmail --rcfile rc.vchimishuk --rcfile rc.geomotiv --rcfile rc.viacheslav88

Network connection is still alive:
$ netstat -tnlp | grep 24207
tcp        0      0 192.168.2.100:37432     213.180.204.212:995     ESTABLISHED 24207/python2

Here is a stack trace:
  File "/bin/getmail", line 934, in <module>
    main()
  File "/bin/getmail", line 898, in main
    success = go(configs, options.idle)
  File "/bin/getmail", line 166, in go
    retriever.select_mailbox(mailbox)
  File "/usr/lib/python2.7/site-packages/getmailcore/_retrieverbases.py", line 1046, in select_mailbox
    self._getmsglist()
  File "/usr/lib/python2.7/site-packages/getmailcore/_retrieverbases.py", line 1057, in _getmsglist
    (response, msglist, octets) = self.conn.uidl()
  File "/usr/lib/python2.7/poplib.py", line 323, in uidl
    return self._longcmd('UIDL')
  File "/usr/lib/python2.7/poplib.py", line 172, in _longcmd
    return self._getlongresp()
  File "/usr/lib/python2.7/poplib.py", line 155, in _getlongresp
    line, o = self._getline()
  File "/usr/lib/python2.7/poplib.py", line 381, in _getline
    self._fillBuffer()
  File "/usr/lib/python2.7/poplib.py", line 371, in _fillBuffer
    localbuf = self.sslobj.read()
  File "/usr/lib/python2.7/ssl.py", line 659, in read
    v = self._sslobj.read(len)
  File "<string>", line 1, in <module>
  File "<string>", line 1, in <module>

Line numbers in stack trace may not be very accurate, I've added some
print statements to print some debug messages.

What I can see from my debug next process happens:
1. getmail sends UIDL command
2. server responds with next line
   +OK 91173 1809030538
3. getmail reads next lines until "." will be returned
   1 169447935979906567
   2 169447935979906566
   3 169447935979906565
   4 169447935979906564
   ...
   35393 161566636631953045
   35394 161566636631953042
   35395 161566636631953025
   // No more lines read. No "."
4. POP3 server stops producing any data, getmail blocks inside read()
   call.

AFAIU, TCP connection is not closed correctly by server (?) and
remains open. I saw it blocked for more then a day.
Maybe we can fix it by setting read timeout for a socket? What do you
think about the situation?

[1] https://mail.yandex.ru/

--
Best regards, Viacheslav Chimishuk
[email protected]
Ukraine, Khmelnitsky