[nightlies] Test failure on Ubuntu 13.10

[dobey]

There is a test failing on Ubuntu 13.10, due to an error message having changed:

python -m testtools.run discover
Tests running...
======================================================================
FAIL: u1db.tests.test_https.TestHttpSyncTargetHttpsSupport.test_cannot_verify_cert(oauth_https)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/build/buildd/u1db-0.1.4+r436/obj-i686-linux-gnu/u1db/tests/test_https.py", line 99, in test_cannot_verify_cert
    self.assertIn("certificate verify failed", str(e))
MismatchError: 'certificate verify failed' not in '[Errno 185090050] _ssl.c:340: error:0B084002:x509 certificate routines:X509_load_cert_crl_file:system lib'

Ran 1595 tests in 7.691s
FAILED (failures=1)