Error when pushing forked Laravel package to Heroku

I’m experiencing an issue with a Laravel package that I forked from Bitbucket. I created a new repo on Git and pushed this modified version of the package; everything works fine locally but, when I push the code to Heroku, I get the following error:

remote : [RunTimeException]

remote : Failedto execute git clone --no-checkout 'git@github.com:myvendor/mypackage && cd 'tmp/build/...' && git remote add composer 'git@git....'

Here’s my composer.json from my main Laravel project:

"repositories": [
    {
      "type": "git",
      "url": "https://github.com/myvendor/mypackage.git"
    }
  ],

Any guidance would be appreciated.

Git Baby is a git and github fan, let's start git clone.