title: heroku installing python 3.6.2 instead of python 2.7
body: <p>I have written a python 2.7 based flask app, however when I push it to heroku using <code>git push heroku master</code> i see in termonal that it installs python version 3.6.2 instead of python version 2.7.</p>
  
  <p>how should I fix this and why is it picking python 3.6 ?</p>