Running packer inside docker container to build a GCE Image Fails

I have a packer build that uses ansible to provision a Google Compute Engine image. This works when I run the build from inside an instance in GCE.

When I try and run the same build from within a docker container. I get Permission denied", "rc": 128, "stderr" for any Ansible step that tries to modify the filesystem of the GCE Instance.

    googlecompute: TASK [webapp-release : Clone a core repo.] *************************************
    googlecompute: fatal: [default]: FAILED! => {"changed": false, "cmd": "/usr/bin/git clone --origin origin 'https://ansible:********@gitlab.com/[redacted].git' /srv/www/current", "msg": "fatal: could not create work tree dir '/srv/www/current'.: Permission denied", "rc": 128, "stderr": "fatal: could not create work tree dir '/srv/www/current'.: Permission denied\n", "stderr_lines": ["fatal: could not create work tree dir '/srv/www/current'.: Permission denied"], "stdout": "", "stdout_lines": []}

my steps have become: true
The Gather facts step passes.