Comment 11 for bug 1514094

So While for me a test formerly triggering the bug was fixed for you it essentially turned from:
  An error occured handling 'bcache1': IOError - [Errno 2] No such file or directory: '/sys/block/bcache1/bcache/cache_mode'
into
  An error occured handling 'bcache1': IOError - [Errno 22] Invalid argument

As Ryan suggested, it would be great if you could add "-vvv" when running in debug mode.
As it will help identifying what exactly failed - like reporting the actual failing command.
*just discussed with Blake on IRC - will be possible*

I made the area around the issue a bit more verbose in my latest push to lp:~paelzer/curtin/fix-1514094-v1 which will trigger enabling -vvv.