title: certificate verify failed with MechanicalSoup
body: <p>I want to retrieve some data from my router using MechanicalSoup. However when I try I get "certificate verify failed". As I see it I have two options</p>
  
  <ol>
  <li>Find a way to disable SSL verification</li>
  <li>Tell MechanicalSoup where it can find the pem file (I created it using "openssl s_connect ....")</li>
  </ol>
  
  <p>My code looks like this so far:</p>
  
  <pre><code>import argparse
  import mechanicalsoup
  from getpass import getpass
  
  parser = argparse.ArgumentParser(description="Get data from router")
  parser.add_argument("-u", "--username", help="User", type=str,
                      required=True)
  parser.add_argument("-s", "--server", help="server", type=str,
                      required=True)
  parser.add_argument("-p", "--port", help="Port", type=str,
                      required=False, default="8443")
  parser.add_argument("-v", "--verbose", help="Verbose output. Add " +
                      "additional v to increase level.",
                      action="count", default=0)
  args = parser.parse_args()
  
  args.password = getpass("Password:")
  
  browser = mechanicalsoup.StatefulBrowser(
      soup_config={'features': 'lxml'},
      raise_on_404=True,
      user_agent='getdata.py/0.1',
  )
  
  browser.set_verbose(args.verbose)
  
  browser.open("https://" + args.server + ":" + args.port)
  </code></pre>
  
  <p>Full error message from end of stack:</p>
  
  <pre><code>Traceback (most recent call last):
    File "perfcreate.py", line 33, in &lt;module&gt;
      browser.open("https://" + args.server + ":" + args.port)
    File "/home/andyw/mypy_env/lib/python3.6/site-packages/mechanicalsoup/stateful_browser.py", line 133, in open
      resp = self.get(url, *args, **kwargs)
    File "/home/andyw/mypy_env/lib/python3.6/site-packages/mechanicalsoup/browser.py", line 124, in get
      response = self.session.get(*args, **kwargs)
    File "/home/andyw/mypy_env/lib/python3.6/site-packages/requests/sessions.py", line 546, in get
      return self.request('GET', url, **kwargs)
    File "/home/andyw/mypy_env/lib/python3.6/site-packages/requests/sessions.py", line 533, in request
      resp = self.send(prep, **send_kwargs)
    File "/home/andyw/mypy_env/lib/python3.6/site-packages/requests/sessions.py", line 646, in send
      r = adapter.send(request, **kwargs)
    File "/home/andyw/mypy_env/lib/python3.6/site-packages/requests/adapters.py", line 514, in send
      raise SSLError(e, request=request)
  requests.exceptions.SSLError: HTTPSConnectionPool(host='192.168.1.1', port=8443): Max retries exceeded with url: / (Caused by SSLError(SSLError("bad handshake: Error([('SSL routines', 'tls_process_server_certificate', 'certificate verify failed')],)",),))
  </code></pre>