'``create_virtualenv`` installs a virtual python whose path does not
include the system python libraries.'

def test_pythonpath(self):

    target_path = FilePath(self.mktemp())
    create_virtualenv(root=target_path)
    output = check_output([target_path.descendant(['bin', 'python']).path, '-c', 'import    sys;    sys.stdout.write("\\n".join(sys.path))'])
    self.assertNotIn('/usr/lib/python2.7/site-packages', output.splitlines())
