I got an error while using "heroku open" command
<p>I'm created a python app on heroku.
After pushing I gave <code>heroku open</code> command and I got an error on browser like this</p>

<pre><code>Application Error

An error occurred in the application and your page could not be served. Please try again in a few moments.

If you are the application owner, check your logs for details.
</code></pre>

<p>I check my logs by using command <code>heroku logs</code> ,I got</p>

<pre><code>2016-08-29T09:53:21.255789+00:00 heroku[api]: Enable Logplex by aparnabalagopal328@gmail.com
2016-08-29T09:53:21.255849+00:00 heroku[api]: Release v2 created by aparnabalagopal328@gmail.com
2016-08-29T09:54:11.279935+00:00 heroku[api]: Attach DATABASE (@ref:postgresql-parallel-41683) by aparnabalagopal328@gmail.com
2016-08-29T09:54:11.280127+00:00 heroku[api]: Release v3 created by aparnabalagopal328@gmail.com
2016-08-29T09:54:11.802177+00:00 heroku[api]: Scale to web=1 by aparnabalagopal328@gmail.com
2016-08-29T09:54:11.802730+00:00 heroku[api]: Deploy 07b053c by aparnabalagopal328@gmail.com
2016-08-29T09:54:11.802825+00:00 heroku[api]: Release v4 created by aparnabalagopal328@gmail.com
2016-08-29T09:54:12.230977+00:00 heroku[slug-compiler]: Slug compilation started
2016-08-29T09:54:12.230983+00:00 heroku[slug-compiler]: Slug compilation finished
2016-08-29T09:54:14.053809+00:00 heroku[web.1]: Starting process with command `gunicorn demoproject.wsgi --log-file -`
2016-08-29T09:54:15.687774+00:00 heroku[web.1]: Process exited with status 127
2016-08-29T09:54:15.625418+00:00 app[web.1]: bash: gunicorn: command not found
2016-08-29T09:54:15.698702+00:00 heroku[web.1]: State changed from starting to crashed
2016-08-29T09:54:15.699101+00:00 heroku[web.1]: State changed from crashed to starting
2016-08-29T09:54:18.068372+00:00 heroku[web.1]: Starting process with command `gunicorn demoproject.wsgi --log-file -`
2016-08-29T09:54:20.311898+00:00 app[web.1]: bash: gunicorn: command not found
2016-08-29T09:54:20.422709+00:00 heroku[web.1]: State changed from starting to crashed
2016-08-29T09:54:20.399025+00:00 heroku[web.1]: Process exited with status 127
2016-08-29T09:54:29.340320+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/" host=desolate-dawn-92822.herokuapp.com request_id=4f6e1b38-3ceb-4fc6-94ae-3f9d714fc0cc fwd="106.66.160.62" dyno= connect= service= status=503 bytes=
2016-08-29T09:54:31.384865+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/favicon.ico" host=desolate-dawn-92822.herokuapp.com request_id=c8a6001a-02b6-489f-b705-84aceff70b54 fwd="106.66.160.62" dyno= connect= service= status=503 bytes=
2016-08-29T09:58:56.842452+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/" host=desolate-dawn-92822.herokuapp.com request_id=af27a7c5-2821-4fe7-9477-2cdc532a3336 fwd="106.66.160.62" dyno= connect= service= status=503 bytes=
2016-08-29T10:08:42.553637+00:00 heroku[api]: Deploy 85408b3 by aparnabalagopal328@gmail.com
2016-08-29T10:08:42.553679+00:00 heroku[api]: Release v5 created by aparnabalagopal328@gmail.com
2016-08-29T10:08:42.740177+00:00 heroku[slug-compiler]: Slug compilation started
2016-08-29T10:08:42.740186+00:00 heroku[slug-compiler]: Slug compilation finished
2016-08-29T10:08:43.684450+00:00 heroku[web.1]: State changed from crashed to starting
2016-08-29T10:08:46.465307+00:00 heroku[web.1]: Starting process with command `gunicorn myapp.wsgi`
2016-08-29T10:08:48.576484+00:00 app[web.1]: bash: gunicorn: command not found
2016-08-29T10:08:48.707427+00:00 heroku[web.1]: State changed from starting to crashed
2016-08-29T10:08:48.708462+00:00 heroku[web.1]: State changed from crashed to starting
2016-08-29T10:08:48.693847+00:00 heroku[web.1]: Process exited with status 127
2016-08-29T10:08:51.121516+00:00 heroku[web.1]: Starting process with command `gunicorn myapp.wsgi`
2016-08-29T10:08:53.420967+00:00 app[web.1]: bash: gunicorn: command not found
2016-08-29T10:08:53.485832+00:00 heroku[web.1]: State changed from starting to crashed
2016-08-29T10:08:53.480263+00:00 heroku[web.1]: Process exited with status 127
2016-08-29T10:08:54.151339+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/" host=desolate-dawn-92822.herokuapp.com request_id=64a8fc46-fe45-4cb9-8d4b-66ef1ce06613 fwd="106.66.160.62" dyno= connect= service= status=503 bytes=
2016-08-29T10:10:27.972626+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/" host=desolate-dawn-92822.herokuapp.com request_id=ed27deb7-9638-4bd4-8dde-1a067e721bd8 fwd="106.66.160.62" dyno= connect= service= status=503 bytes=
2016-08-29T10:25:36.636851+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/" host=desolate-dawn-92822.herokuapp.com request_id=294294a1-d3fb-415c-a241-a5dd5856ca1c fwd="106.66.160.62" dyno= connect= service= status=503 bytes=
2016-08-29T10:34:37.538080+00:00 heroku[web.1]: State changed from crashed to starting
2016-08-29T10:34:40.686186+00:00 heroku[web.1]: Starting process with command `gunicorn myapp.wsgi`
2016-08-29T10:34:42.873466+00:00 heroku[web.1]: Process exited with status 127
2016-08-29T10:34:42.915769+00:00 heroku[web.1]: State changed from starting to crashed
2016-08-29T10:34:42.787502+00:00 app[web.1]: bash: gunicorn: command not found
2016-08-29T11:25:00.207326+00:00 heroku[web.1]: State changed from crashed to starting
2016-08-29T11:25:02.610880+00:00 heroku[web.1]: Starting process with command `gunicorn myapp.wsgi`
2016-08-29T11:25:04.177373+00:00 app[web.1]: bash: gunicorn: command not found
2016-08-29T11:25:04.259289+00:00 heroku[web.1]: State changed from starting to crashed
2016-08-29T11:25:04.244018+00:00 heroku[web.1]: Process exited with status 127
2016-08-29T12:49:30.399226+00:00 heroku[web.1]: State changed from crashed to starting
2016-08-29T12:49:32.974142+00:00 heroku[web.1]: Starting process with command `gunicorn myapp.wsgi`
2016-08-29T12:49:34.619515+00:00 app[web.1]: bash: gunicorn: command not found
2016-08-29T12:49:34.664374+00:00 heroku[web.1]: Process exited with status 127
2016-08-29T12:49:34.654539+00:00 heroku[web.1]: State changed from starting to crashed
2016-08-29T14:27:57.820573+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/" host=desolate-dawn-92822.herokuapp.com request_id=e19b82f3-ee8d-48ba-81d3-f8b9f931ec08 fwd="106.66.175.169" dyno= connect= service= status=503 bytes=
2016-08-29T14:27:58.187626+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/favicon.ico" host=desolate-dawn-92822.herokuapp.com request_id=846c1921-f4e4-4fd6-bf4d-f8d3b3c09d84 fwd="106.66.175.169" dyno= connect= service= status=503 bytes=
2016-08-29T14:28:11.624391+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/" host=desolate-dawn-92822.herokuapp.com request_id=1104d918-c899-4ba8-a49c-90941ece26cb fwd="106.66.175.169" dyno= connect= service= status=503 bytes=
</code></pre>

<p>The link address of my app is 
   <a href="https://desolate-dawn-92822.herokuapp.com/" rel="nofollow">https://desolate-dawn-92822.herokuapp.com/</a></p>

<p>It seems that <code>gunicorn</code> is missing. You should add <code>gunicorn</code> to your <code>requirements.txt</code> and deploy your project again to Heroku. </p>

python git heroku