Unable to start R kernel in notebook

[sebbacon]

When building in Gihub environment (example log), the ir kernelspec that's installed when we build locally is not there:

{
  "kernelspecs": {
    "python3": {
      "resource_dir": "/root/.pyenv/versions/3.8.1/share/jupyter/kernels/python3",
      "spec": {
        "argv": [
          "python",
          "-m",
          "ipykernel_launcher",
          "-f",
          "{connection_file}"
        ],
        "env": {},
        "display_name": "Python 3",
        "language": "python",
        "interrupt_mode": "signal",
        "metadata": {}
      }
    },
    "bash": {
      "resource_dir": "/usr/local/share/jupyter/kernels/bash",
      "spec": {
        "argv": [
          "/root/.pyenv/versions/3.8.1/bin/python",
          "-m",
          "bash_kernel",
          "-f",
          "{connection_file}"
        ],
        "env": {
          "PS1": "$"
        },
        "display_name": "Bash",
        "language": "bash",
        "interrupt_mode": "signal",
        "metadata": {}
      }
    }
  }
}