My problem is exactly like How do I install in-house requirements for Python Heroku projects? and How to customize pip's requirements.txt in Heroku on
I created a buildpack to solve this problem using a custom ssh key stored as an environment variable. As the buildpack is technology agnostic, it can be used to download dependencies using any tool like composer for php, bundler for ruby, npm for javascript, etc: https://github.com/simon0191/custom-ssh-key-buildpack
Add the buildpack to your app:
$ heroku buildpacks:add --index 1 https://github.com/simon0191/custom-ssh-key-buildpack
Generate a new SSH key (lets say you named it deploy_key)
Add the public key to your private repository account. For example:
Github: https://help.github.com/articles/adding-a-new-ssh-key-to-your-github-account/
Bitbucket: https://confluence.atlassian.com/bitbucket/add-an-ssh-key-to-an-account-302811853.html
Encode the private key as a base64 string and add it as the CUSTOM_SSH_KEY
environment variable of the heroku app.
Make a comma separated list of the hosts for which the ssh key should be used and add it as the CUSTOM_SSH_KEY_HOSTS
environment variable of the heroku app.
# MacOS
$ heroku config:set CUSTOM_SSH_KEY=$(base64 --input ~/.ssh/deploy_key) CUSTOM_SSH_KEY_HOSTS=bitbucket.org,github.com
# Ubuntu
$ heroku config:set CUSTOM_SSH_KEY=$(base64 ~/.ssh/deploy_key) CUSTOM_SSH_KEY_HOSTS=bitbucket.org,github.com