title: Python requests throwing SSLError while using local certificate
body: <p>I'm writing a script to a server and verify it's certificate. If I write the script using sockets it works fine:</p>
  
  <pre><code>import socket, ssl, pprint
  
  s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
  ssl_sock = ssl.wrap_socket(s,
                             ca_certs="mule.crt",
                             cert_reqs=ssl.CERT_REQUIRED)
  
  ssl_sock.connect(('localhost', 8081))
  
  message = "GET /api HTTP/1.1\r\nHost:localhost\r\n\r\n"
  ssl_sock.write(bytes(message, 'UTF-8'))
  
  data = ssl_sock.read().decode("utf-8")
  print(data)
  
  ssl_sock.close()
  </code></pre>
  
  <p>If I try to do a similar thing using requests:</p>
  
  <pre><code>import requests
  
  r = requests.get('https://localhost:8081/api', cert=r'C:\path\to\cert\mule.crt')
  
  print(r.status_code)
  print(r.text)
  </code></pre>
  
  <p>This throws:</p>
  
  <pre><code>Traceback (most recent call last):
    File "C:\path\to\py\ssltest.py", line 4, in &lt;module&gt;
      r = requests.get('https://localhost:8081/api', cert=r'C:\path\to\cert\mule.crt')
    File "C:\Python34\lib\site-packages\requests\api.py", line 69, in get
      return request('get', url, params=params, **kwargs)
    File "C:\Python34\lib\site-packages\requests\api.py", line 50, in request
      response = session.request(method=method, url=url, **kwargs)
    File "C:\Python34\lib\site-packages\requests\sessions.py", line 465, in request
      resp = self.send(prep, **send_kwargs)
    File "C:\Python34\lib\site-packages\requests\sessions.py", line 573, in send
      r = adapter.send(request, **kwargs)
    File "C:\Python34\lib\site-packages\requests\adapters.py", line 431, in send
      raise SSLError(e, request=request)
  requests.exceptions.SSLError: [SSL] PEM lib (_ssl.c:2536)
  </code></pre>
  
  <p>Any ideas what I might be doing wrong?</p>