Fatal: run_command returned non-zero status

When attempting to run a deployment, you may run into the following error during the build step, when we try to checkout your repository at the end revision:

Checking out working copy of your repository at 
123abc (master)

An error occurred

Warning: Permanently added 'bitbucket.org,2406:da00:ff00::22cd:e0db' 
(RSA) to the list of known hosts. repository does not 
exist. fatal: Could not read from remote repository. 
Please make sure you have the correct access rights 
and the repository exists. fatal: run_command returned 
non-zero status for submodule/path.

This specifically happens when trying to fetch code from the source repository referenced in a submodule. If the source repository has changed in any way, such as being renamed, the above error will occur.

You'll need to check your .gitmodules file to ensure the repository URL is correct, and if necessary change it, then push the commit to your repository.