Fails: Command 01_mount failed

On using this I get the error:
`[ERROR] An error occurred during execution of command [app-deploy] - [PreBuildEbExtension]. Stop running the command. Error: EbExtension build failed. Please refer to /var/log/cfn-init.log for more details.`

In cfn-init.log this leads to:
`[ERROR] Unhandled exception during build: Command 01_mount failed`

To fix this:
1. Create an EFS
2. Set new Environment property as EFS_VOLUME_ID with the value of the File System ID

There will be a config change in efs-mount.config to fix this which will need looking at