Make the symmetric-enc example an example
Making some minor tweaks to the doc example for symmetric encryption so
it is an actual, runable example.
diff --git a/docs/hazmat/primitives/symmetric-encryption.rst b/docs/hazmat/primitives/symmetric-encryption.rst
index 8d3769f..8323028 100644
--- a/docs/hazmat/primitives/symmetric-encryption.rst
+++ b/docs/hazmat/primitives/symmetric-encryption.rst
@@ -35,10 +35,12 @@
.. doctest::
+ >>> import os
>>> from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
>>> from cryptography.hazmat.backends import default_backend
>>> backend = default_backend()
- >>> cipher = Cipher(algorithms.AES(key), modes.CBC(iv), backend=backend)
+ >>> key = os.urandom(24)
+ >>> cipher = Cipher(algorithms.AES(key), modes.CBC(os.urandom(16)), backend=backend)
>>> encryptor = cipher.encryptor()
>>> ct = encryptor.update(b"a secret message") + encryptor.finalize()
>>> decryptor = cipher.decryptor()