Unlike the older ContextFactory classes, CertificateOptions has somewhat
more modern requirements not dictated by HTTP. Specifically, the method
is TLSv1 and certificates are required.
>>> import twisted
>>> import twisted.internet.ssl
>>> ssl.CertificateOptions()
Traceback (most recent call last):
File "<stdin>", line 1, in ?
NameError: name 'ssl' is not defined
>>> twisted.__version__
'2.4.0'
When was that added?