title: (centos6.6) before updating python2.7.3 ,it is python 2.6.6. When running pybot --version,errors came out
body: <p>(centos6.6) before updating python2.7.3 ,it is python 2.6.6. When running <code>pybot --version</code>, errors came out as follows.</p>
  
  <p>I want to install the test environment of python 2.7.3 and robot framework 2.7.6 and paramiko-1.7.4 and pycrypto-2.6</p>
  
  <blockquote>
    <p>[root@localhost robotframework-2.7.6]# pybot --version<br>
    Traceback (most recent call last):<br>
      File "/usr/bin/pybot", line 4, in <br>
        from robot import run_cli<br>
      File "/usr/lib/python2.7/site-packages/robot/__init__.py", line 22, in <br>
        from robot.rebot import rebot, rebot_cli<br>
      File "/usr/lib/python2.7/site-packages/robot/rebot.py", line 268, in <br>
        from robot.conf import RebotSettings<br>
      File "/usr/lib/python2.7/site-packages/robot/conf/__init__.py", line 17, in <br>
        from .settings import RobotSettings, RebotSettings<br>
      File "/usr/lib/python2.7/site-packages/robot/conf/settings.py", line 17, in <br>
        from robot import utils<br>
      File "/usr/lib/python2.7/site-packages/robot/utils/__init__.py", line 23, in <br>
        from .compress import compress_text<br>
      File "/usr/lib/python2.7/site-packages/robot/utils/compress.py", line 25, in <br>
        import zlib<br>
    ImportError: No module named zlib</p>
  </blockquote>