Git Clone - repository access denied - Please make sure you have the correct access rights

Git Clone step fails with:

...
e[34;1mGit clone repositorye[0m
=> git "init"
=> git "remote" "add" "origin" "REDACTED"
=> git "fetch"
e[33;1m0 attempt failed:e[0m
Warning: Permanently added '...,...' (RSA) to the list of known hosts.
repository access denied.
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.
...

The key part of the log / issue is:

repository access denied.
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

This means that the SSH key registered for your app on bitrise.io does not have access to / is not allowed to access the repository.

Please make sure that the SSH key (which you can find on the app’s Settings tab on bitrise.io) is registered on your source code hosting service.

Related setup guide: http://devcenter.bitrise.io/adding-a-new-app/setting-up-ssh-keys/#manual-setup

P.S.: if you have submodules too, please check this guide: http://devcenter.bitrise.io/faq/adding-projects-with-submodules/ which explains how you can grant access to all the relevant repos for bitrise.io