Issue #359: Timeout of gunicorn worker under Python 3 (conservancy/kallithea)

[vyom]

New issue 359: Timeout of gunicorn worker under Python 3
https://bitbucket.org/conservancy/kallithea/issues/359/timeout-of-gunicorn-worker-under-python-3

vyom:

After moving to new Kallithea version with Python 3, unable to clone repository, it gives worker TIMEOUT error and operations are rolled back, the same clone works with Python 2 and older version. In logs there is no error.

```
http authorization required for https://hg.xxxxxxxx.com/test/test-repository
realm: Kallithea
user: kallithea
password:
files [====>                                                                                        ]  358/6509 7m18sdestination directory: test-repository
requesting all changes
adding changesets
adding manifests
adding file changes
transaction abort!
rollback completed
abort: HTTP request error (incomplete response)
(this may be an intermittent network failure; if the error persists, consider contacting the network or server operator)
```

The Gunicorn service log is:

```plaintext
Feb 13 22:37:23 kallithea-5-2 gunicorn[7755]: [2020-02-13 22:37:23 +0800] [7755] [INFO] Starting gunicorn 20.0.4
Feb 13 22:37:23 kallithea-5-2 gunicorn[7755]: [2020-02-13 22:37:23 +0800] [7755] [INFO] Listening at: http://0.0.0.0:5000 (7755)
Feb 13 22:37:23 kallithea-5-2 gunicorn[7755]: [2020-02-13 22:37:23 +0800] [7755] [INFO] Using worker: sync
Feb 13 22:37:23 kallithea-5-2 gunicorn[7755]: [2020-02-13 22:37:23 +0800] [7758] [INFO] Booting worker with pid: 7758
Feb 13 22:42:05 kallithea-5-2 gunicorn[7755]: [2020-02-13 22:42:05 +0800] [7755] [CRITICAL] WORKER TIMEOUT (pid:7758)
Feb 13 22:42:05 kallithea-5-2 gunicorn[7755]: [2020-02-13 22:42:05 +0800] [7758] [INFO] Worker exiting (pid: 7758)
Feb 13 22:42:05 kallithea-5-2 gunicorn[7755]: [2020-02-13 22:42:05 +0800] [8876] [INFO] Booting worker with pid: 8876
```

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