title: why tests fails when testing python-glanceclients?
body: <p>i am using python 2.6.6, why run_tests tried to find python 2.7?</p>
  
  <pre><code>(os)mirror0@lab:~/tmp/python-glanceclient$ ./run_tests.sh
  GLOB sdist-make: /home/mirror0/tmp/python-glanceclient/setup.py
  py27 create: /home/mirror0/tmp/python-glanceclient/.tox/py27
  ERROR: InterpreterNotFound: python2.7
  ___________________________________ summary ____________________________________
  ERROR:   py27: InterpreterNotFound: python2.7
  (os)mirror0@lab:~/tmp/python-glanceclient$ python -V
  Python 2.6.6
  </code></pre>