utopic txaws tests: exceptions.TypeError: 'X509' object is not iterable

[ERROR]
Traceback (most recent call last):
  File "/build/buildd/txaws-0.2.3+157/txaws/client/tests/test_base.py", line 236, in test_ssl_hostname_verification
    query.get_page("https://example.com/file")
  File "/build/buildd/txaws-0.2.3+157/txaws/client/base.py", line 239, in get_page
    self.body_producer)
  File "/usr/lib/python2.7/dist-packages/twisted/web/client.py", line 1471, in request
    parsedURI.port)
  File "/usr/lib/python2.7/dist-packages/twisted/web/client.py", line 1451, in _getEndpoint
    tlsPolicy = self._policyForHTTPS.creatorForNetloc(host, port)
  File "/usr/lib/python2.7/dist-packages/twisted/web/client.py", line 958, in creatorForNetloc
    context = self._webContextFactory.getContext(hostname, port)
  File "/build/buildd/txaws-0.2.3+157/txaws/client/base.py", line 164, in getContext
    return VerifyingContextFactory.getContext(self)
  File "/usr/lib/python2.7/dist-packages/twisted/internet/_sslverify.py", line 1429, in getContext
    self._context = self._makeContext()
  File "/build/buildd/txaws-0.2.3+157/txaws/client/ssl.py", line 79, in _makeContext
    context = CertificateOptions._makeContext(self)
  File "/usr/lib/python2.7/dist-packages/twisted/internet/_sslverify.py", line 1452, in _makeContext
    self.trustRoot._addCACertsToContext(ctx)
  File "/usr/lib/python2.7/dist-packages/twisted/internet/_sslverify.py", line 884, in _addCACertsToContext
    for cert in self._caCerts:
exceptions.TypeError: 'X509' object is not iterable

txaws.client.tests.test_base.BaseQueryTestCase.test_ssl_hostname_verification