Serial number randomization with improved portability.

No exception handling required this time.

acme/acme/crypto_util.py

@@ -1,4 +1,5 @@
 """Crypto utilities."""
+import binascii
 import contextlib
 import logging
 import re
@@ -203,11 +204,7 @@ def gen_ss_cert(key, domains, not_before=None,
     """
     assert domains, "Must provide one or more hostnames for the cert."
     cert = OpenSSL.crypto.X509()
-    try:
-        cert.set_serial_number(int(OpenSSL.rand.bytes(16).encode("hex"), 16))
-    except AttributeError:
-        # pylint: disable=E1101
-        cert.set_serial_number(int.from_bytes(OpenSSL.rand.bytes(16), 'big'))
+    cert.set_serial_number(int(binascii.hexlify(OpenSSL.rand.bytes(16)), 16))
     cert.set_version(2)
 
     extensions = [