Python urllib3 urlopen does not use retries whith specific errors

Why urlopen from urllib3 does not retry when it hits a ReadTimeoutError ? Am I missing something ? I can get around this by using my own retry code, but I would prefer to use the one from the module.

I've even tried to explicitely put retries=3 as an argument of HTTPSConnectionPool.request() but it does not help...

Here's my code:

conn = urllib3.HTTPConnectionPool(host, port=port)
return conn.request(method, api_url, data, retries=3, 
                    timeout=urllib3.Timeout(connect=2, read=3))

Thanks !

EDIT:

Now, the response with some debug info (it's a log from openERP):

2014-06-18 08:36:42,791 5585 DEBUG test 
openerp.addons.myaddon.xml_request.xml_request: args prepared
2014-06-18 08:36:42,791 DEBUG Added an stderr logging handler to logger: 
urllib3
2014-06-18 08:36:42,791 5585 DEBUG test urllib3: Added an stderr logging 
handler to logger: urllib3
2014-06-18 08:36:42,792 INFO Starting new HTTPS connection (1): 
some.host.com
2014-06-18 08:36:42,792 5585 INFO test urllib3.connectionpool: Starting new 
HTTPS connection (1): some.host.com
2014-06-18 08:36:43,699 DEBUG Setting read timeout to 10
2014-06-18 08:36:43,699 5585 DEBUG test urllib3.connectionpool: Setting read 
timeout to 10
2014-06-18 08:36:53,722 5585 ERROR test openerp.osv.osv: Uncaught exception
Traceback (most recent call last):
  File "/home/openerp/server/openerp/osv/osv.py", line 132, in wrapper
    return f(self, dbname, *args, **kwargs)
  File "/home/openerp/server/openerp/osv/osv.py", line 199, in execute
    res = self.execute_cr(cr, uid, obj, method, *args, **kw)
  File "/home/openerp/server/openerp/osv/osv.py", line 187, in execute_cr
    return getattr(object, method)(cr, uid, *args, **kw)
  File "/home/openerp/custom_addons/myaddon/xml_request/xml_request.py", 
  line 260, in button_test
    self.request(cr, uid, ids[0], data, context=context)
  File "/home/openerp/custom_addons/myaddon/xml_request/xml_request.py", 
  line 234, in request
    config_rec.xml_port, 'POST', api_url, vals)
  File "/home/openerp/custom_addons/myaddon/xml_request/xml_request.py", 
  line 208, in connAndReq
    timeout=urllib3.Timeout(connect=5, read=10))
  File "/usr/lib/python2.7/dist-packages/urllib3/request.py", line 79, in 
  request
    **urlopen_kw)
  File "/usr/lib/python2.7/dist-packages/urllib3/request.py", line 142, in 
  request_encode_body
    **urlopen_kw)
  File "/usr/lib/python2.7/dist-packages/urllib3/connectionpool.py", line 
  574, in urlopen
    raise ReadTimeoutError(self, url, "Read timed out.")
ReadTimeoutError: HTTPSConnectionPool(host=u'some.host.com', port=443): Read 
timed out.

As you can see, the ReadTimeoutError is thrown just after the expiration time, with no retries.