SSLError when using requests.session

Summary.

Getting a SSLError while using requests.session to send a POST Request. OpenSSL SSL_connect: SSL_ERROR_SYSCALL in connection to dev.domain.nl:443 
When using requests sessions to connect to a https url , requests throws a SSLError

Some background
- I have not added any certificates
- The project works locally but after deployment to kubernetes, from inside the container - the post request is not being sent to the url
- verify=false does not work either

What I am using:
Python 2.7.12
Flask==0.12.2
Kubernetes 
requests latest

## Expected Result

Get HTTP Response code 200 after sending a POST request

## Actual Result

Traceback (most recent call last):
  File "/usr/local/lib/python2.7/threading.py", line 801, in __bootstrap_inner
    self.run()
  File "/usr/local/lib/python2.7/threading.py", line 1073, in run
    self.function(*self.args, **self.kwargs)
  File "app.py", line 136, in main
    generatePost()
  File "app.py", line 127, in generatePost
    resp = testlibrary.test_post()
  File "/web/testlibrary.py", line 138, in test_post
    response = sess.post(url, headers= header, params= getpara, data= json.dumps(data),verify=False)
  File "/usr/local/lib/python2.7/site-packages/requests/sessions.py", line 559, in post
    return self.request('POST', url, data=data, json=json, **kwargs)
  File "/usr/local/lib/python2.7/site-packages/requests/sessions.py", line 512, in request
    resp = self.send(prep, **send_kwargs)
  File "/usr/local/lib/python2.7/site-packages/requests/sessions.py", line 622, in send
    r = adapter.send(request, **kwargs)
  File "/usr/local/lib/python2.7/site-packages/requests/adapters.py", line 511, in send
    raise SSLError(e, request=request)
SSLError: HTTPSConnectionPool(host='dev.domain.nl', port=443): Max retries exceeded with url: /ingestion?LrnDevEui=0059AC0000152A03&LrnFPort=1&LrnInfos=TWA_100006356.873.AS-1-135680630&AS_ID=testserver&Time=2018-06-22T11%3A41%3A08.163%2B02%3A00&Token=1765b08354dfdec (Caused by SSLError(SSLEOFError(8, u'EOF occurred in violation of protocol (_ssl.c:661)'),))


## Reproduction Steps
``
```
import requests
from flask import Flask, request, jsonify
from requests import Request, Session

sess = requests.Session()
adapter = requests.adapters.HTTPAdapter(max_retries = 200)
sess.mount('http://', adapter)
sess.mount('https://', adapter)
sess.cert ='/usr/local/lib/python2.7/site-packages/certifi/cacert.pem'


def test_post():
    url = 'https://dev.domain.nl/ingestion/?'
    header = {'Content-Type': 'application/json', 'Accept': 'application/json'}
    response = sess.post(url, headers= header, params= somepara, data= json.dumps(data))
    print response.status_code
    return response.status_code

def main():
    threading.Timer(10.0, main).start()
    test_post()

if __name__ == '__main__':
    main()
    app.run(host="0.0.0.0", debug=True, port=5001, threaded=True)
```
```

System Info
```
Python 2.7.12
Flask==0.12.2
Kubernetes
```


@Lukasa Do you think you can help me? :) 

Hi there! Thanks for opening this issue. Unfortunately, it seems this is a request for help instead of a report of a defect in the project. Please use [StackOverflow](https://stackoverflow.com) for general usage questions instead and only report defects here.

---

As indicated by

```
Caused by SSLError(SSLEOFError(8, u'EOF occurred in violation of protocol (_ssl.c:661)')
```

This is not a Requests bug. Something about your container networking is causing this violation of the protocol.