TypeError when quitting with sys.Exit()

[lstep]

When running this simple program:

import etcd
import sys

if __name__ == "__main__":
    client = etcd.Client(port=2379)
    sys.exit()

I get an error when exiting. Other functions (read()) work fine:

Exception ignored in: <bound method Client.__del__ of <etcd.client.Client object at 0x7ff7739bae48>>
Traceback (most recent call last):
  File "/tmp/ETCD/lib/python3.4/site-packages/python_etcd-0.4.3-py3.4.egg/etcd/client.py", line 226, in __del__
  File "/tmp/ETCD/lib/python3.4/site-packages/urllib3-1.16-py3.4.egg/urllib3/poolmanager.py", line 160, in clear
  File "/tmp/ETCD/lib/python3.4/site-packages/urllib3-1.16-py3.4.egg/urllib3/_collections.py", line 89, in clear
TypeError: 'NoneType' object is not callable

I'm using the current version of python-etcd from the repository (0.4.3) with etcd 3.0.3 and python 3.4.3.
If I don't put a sys.exit(), it quits without any exception, all working fine.

[lavagetto]

This looks like a problem in urllib3's poolmanager. I'll take a look later.

[cenkalti]

Duplicate of #179