Cloning plugins from private repositories fail with bk local

[pecigonzalo]

While trying to test a pipeline locally, Im facing the following problem:

~~~ Preparing plugins
# Plugin "github.com/ORG/vagrant-buildkite-plugin.git" will be checked out to "/tmp/buildkite-plugins-332468116/github-com-ORG-vagrant-buildkite-plugin-git-main"
$ cd /tmp/buildkite-plugins-332468116/github-com-ORG-vagrant-buildkite-plugin-git-main
# Switching to the plugin directory
# Host "github.com" already in list of known hosts at "/home/USER/.ssh/known_hosts"
$ git clone -v -- ssh://git@github.com/ORG/vagrant-buildkite-plugin.git .
Cloning into '.'...
git@github.com: Permission denied (publickey).
fatal: Could not read from remote repository.

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

The pipeline config is:

steps:
  - commands:
      - ./test/e2e/test.sh
    plugins:
      - ssh://git@github.com/ORG/vagrant-buildkite-plugin.git#main:
          plugins:
            - vagrant-google

If I manually run git clone -v -- ssh://git@github.com/ORG/vagrant-buildkite-plugin.git . it does work.