Fix for an issue where a call to the Requests.post never returned bec…

…ause of a bug in the cryptography module.

ref pyca/cryptography/#2299

django_auth_adfs/backend.py

@@ -1,7 +1,7 @@
 from os.path import isfile
 
 import jwt
-from cryptography.hazmat.backends import default_backend
+from cryptography.hazmat.backends.openssl.backend import backend
 from cryptography.x509 import load_pem_x509_certificate
 from django.contrib.auth import get_user_model
 from django.contrib.auth.backends import ModelBackend
@@ -25,7 +25,8 @@ def __init__(self):
                     certificate = file.read()
             if isinstance(certificate, str):
                 certificate = certificate.encode()
-            cert_obj = load_pem_x509_certificate(certificate, default_backend())
+            backend.activate_builtin_random()
+            cert_obj = load_pem_x509_certificate(certificate, backend)
             self._public_key = cert_obj.public_key()
         else:
             raise ImproperlyConfigured("ADFS token signing certificate not set")