error: failed to push some refs to 'https://git.heroku.com/immense-stream-52796.git code example

Example: error: failed to push some refs to 'https://git.heroku.com/obscure-dawn-05608.git'

$ rake assets:precompile
$ git add .
$ git commit -m "Add precompiled assets for Heroku"
$ git push heroku master