title: Heroku Python failed to detect app matching buildpack
body: <p>I can't deploy my Flask app to Heroku...
  I've searched in every thread I can and nothing worked for me : add a runtime.txt, set a buildpack. I don't know what can be wrong now.</p>
  
  <p>Here is my root directory for the app : </p>
  
  <pre><code>Project
   - .git
   - Procfile
   - Readme.md
   - app
   - config.py
   - requirements.txt
   - runtime.txt
   - web.py
  </code></pre>
  
  <p>Here's the content of requirements.txt:</p>
  
  <pre><code>appdirs==1.4.3
  click==6.7
  Flask==0.12.1
  Flask-WTF==0.14.2
  itsdangerous==0.24
  Jinja2==2.9.5
  MarkupSafe==1.0
  packaging==16.8
  pyparsing==2.2.0
  six==1.10.0
  Werkzeug==0.12.1
  WTForms==2.1
  </code></pre>
  
  <p>The Procfile : </p>
  
  <pre><code>web: python web.py
  </code></pre>
  
  <p>And the runtime.txt:</p>
  
  <pre><code>python-2.7.13
  </code></pre>
  
  <p>When I do <code>git push heroku master</code>, it prints:</p>
  
  <pre><code>remote: Compressing source files... done.
  remote: Building source:
  remote:
  remote:  !     No default language could be detected for this app.
  remote:             HINT: This occurs when Heroku cannot detect the buildpack to use for this application automatically.
  remote:             See https://devcenter.heroku.com/articles/buildpacks
  remote:
  remote:  !     Push failed
  remote: Verifying deploy...
  remote:
  remote: !   Push rejected to appname.
  remote:
  </code></pre>
  
  <p>I tried to add a buildpack with <code>heroku buildpacks:add heroku/Python</code> but then it says that it can't detect app for python buildpack.</p>
  
  <p>What could I possibly did wrong ?</p>