raise exception_class(message, screen, stacktrace)
     selenium.common.exceptions.WebDriverException: Message: Reached error page: about:neterror?e=nss

   ff_profile = webdriver.FirefoxProfile()
   ff_profile.set_preference("network.proxy.type", 1)
   ff_profile.set_preference("network.proxy.http", 'www-cache.reith.bbc.co.uk')
   ff_profile.set_preference("network.proxy.http_port", 80)
   ff_profile.set_preference("network.proxy.ssl", 'www-cache.reith.bbc.co.uk')
   ff_profile.set_preference("network.proxy.ssl_port", 80)
   ff_profile.set_preference("webdriver_accept_untrusted_certs", True)
   ff_profile.set_preference("webdriver_assume_untrusted_certs", False)
   ff_profile.trustAllSSLCertificates = True
   ff_profile.update_preferences()
   caps = DesiredCapabilities.FIREFOX.copy()
   caps['acceptSslCerts'] = True
   caps['commandLineFlags'] = "--ssl-certificates-path=/etc/pki/tls/certs/ca-bundle.pem --ssl-client-certificate-file=/etc/pki/tls/certs/client.pem --ssl-client-key-file=/etc/pki/tls/private/client.key"
   options = Options()
   options.set_headless(headless=True)
   driver = webdriver.Firefox(firefox_profile=ff_profile, firefox_options=options, capabilities=caps)

   driver.implicitly_wait(10)

   driver.get(url)

Centos 7 Firefox 57 Gecko Driver 0.20.1 I am trying to access a url with SSL certificates, but getting the following error raise exception_class(message, screen, stacktrace) selenium.common.exceptions.WebDriverException: Message: Reached error page: about:neterror?e=nss Failure2&u=https%3A//pagemon-controller.int.api.bbci.co.uk/tests%3Fpage_size%3D1&c=UTF-8&f=regular&d=A n%20error%20occurred%20during%20a%20connection%20to%20pagemon-controller.int.api.bbci.co.uk.%0A%0ASSL% 20peer%20was%20unable%20to%20negotiate%20an%20acceptable%20set%20of%20security%20parameters.%0A%0AErro r%20code%3A%20%3Ca%20id%3D%22errorCode%22%20title%3D%22SSL_ERROR_HANDSHAKE_FAILURE_ALERT%22%3ESSL_ERRO R_HANDSHAKE_FAILURE_ALERT%3C/a%3E%0A I think I have tried every permutation of setting, currently I have the code as ff_profile = webdriver.FirefoxProfile() ff_profile.set_preference("network.proxy.type", 1) ff_profile.set_preference("network.proxy.http", 'www-cache.reith.bbc.co.uk') ff_profile.set_preference("network.proxy.http_port", 80) ff_profile.set_preference("network.proxy.ssl", 'www-cache.reith.bbc.co.uk') ff_profile.set_preference("network.proxy.ssl_port", 80) ff_profile.set_preference("webdriver_accept_untrusted_certs", True) ff_profile.set_preference("webdriver_assume_untrusted_certs", False) ff_profile.trustAllSSLCertificates = True ff_profile.update_preferences() caps = DesiredCapabilities.FIREFOX.copy() caps['acceptSslCerts'] = True caps['commandLineFlags'] = "--ssl-certificates-path=/etc/pki/tls/certs/ca-bundle.pem --ssl-client-certificate-file=/etc/pki/tls/certs/client.pem --ssl-client-key-file=/etc/pki/tls/private/client.key" options = Options() options.set_headless(headless=True) driver = webdriver.Firefox(firefox_profile=ff_profile, firefox_options=options, capabilities=caps) driver.implicitly_wait(10) driver.get(url)