tests: fixed test too dependent on actual exception wording
On one of the machines I use to run the tests prior to submission,
the default Python is 2.7.5, with the following wording:
must be encoded string without NULL bytes, not str
This third form (and possible future ones) are motivation to
use a wider catching regexp.
# name space package to host third party extensions
from __future__ import absolute_import
import pkgutil
__path__ = pkgutil.extend_path(__path__, __name__)