kube-spawn up not working due to missing flatcar-channel

[tiagomlalves]

Running kube-spawn fails due to missing flatcar-channel variable. Most likely a regression from latest change done in kube-spawn start.

Steps:
$ sudo kube-spawn up -n

Error:

Copying files for cluster ...
Generating configuration files from templates ...
Cluster default created
Could not set limit: Failed to adjust loopback limit: Is a directory image resize failed: qemu-img not installed: exec: "qemu-img": executable file not found in $PATH
Resize '/var/lib/machines' of 'max'
pulling flatcar image...
Enqueued transfer job 1. Press C-c to continue download in background.
Pulling 'https://.release.flatcar-linux.net/amd64-usr/current/flatcar_developer_container.bin.bz2', > saving as 'flatcar'.
Transfer failed: Couldn't resolve host name
Failed to retrieve image file. (Wrong URL?)
Exiting.
Failed to start cluster: error running machinectl pull-raw: exit status 1