Old thread but I just ran into the same issue. Home Assistant refused to boot even after I had it check my config file and said it was good.
I’m running HomeAssistant (formerly Hass.io according to this) via VirtualBox to experiment with but the same steps should work as long as you have access to the command line of whatever machine you’ve installed it on (even a Pi with an SD card install).
After running login from the command prompt I was given when it booted up (where it seemed to be restricted to just ha commands) I got to the host prompt and started playing around with docker inspect to see where the docker images that home assistant uses map their data too. This was the revealing command:
docker inspect -f '{{ .Mounts }}' homeassistant
The key piece of the output was:
{ bind /mnt/data/supervisor/homeassistant /config ...
So the /config directory inside the main docker container (same file structure you get when using the SSH Add-on in the Home Assistant UI) is mapped to /mnt/data/supervisor/homeassistant/ in the host OS (i.e. the SD card or VM or wherever you installed it).
I edited the config file with the vi command (i.e. vi /mnt/data/supervisor/homeassistant/), undid my latest changes, rebooted the VM…
Problem solved