title: can't detect default python version
body: <pre><code>~$ python
  bash: python: command not found
  </code></pre>
  
  <p><strong>while running python2 and python 3 its showing different versions.</strong></p>
  
  <pre><code>~$ python2
  Python 2.7.6 (default, Jun 22 2015, 17:58:13) 
  [GCC 4.8.2] on linux2
  Type "help", "copyright", "credits" or "license" for more information.
  
  ~$ python3
  Python 3.4.0 (default, Jun 19 2015, 14:20:21) 
  [GCC 4.8.2] on linux
  Type "help", "copyright", "credits" or "license" for more information.
  </code></pre>
  
  <p>i think somehow default python link is broken. i can't seem to access ubuntu software center also.</p>
  
  <p>Please suggest a way to fix this.</p>