Error when building dependent containers simultaneously

[tailhook]

Config:

containers:

  node:
    setup:
    - !Alpine v3.3
    - !Install [alpine-base, make]
    - !NpmDependencies
    environ:
      NODE_PATH: /usr/lib/node_modules
      HOME: /tmp

  doc:
    setup:
    - !Container node
    - !Install [py-sphinx, py-sphinx_rtd_theme]

Perhaps, something wrong with cache directory mounts. Here is an error:

OK: 93 MiB in 48 packages
OK: 93 MiB in 48 packages
ERROR:vagga::builder: Error building container "doc": Can't unmount /vagga/root/etc/apk/cache : No such file or directory (os error 2)
ERROR:vagga::wrapper: Error executing _build: Builder exited with code 1

[tailhook]

I've retried it and it looks okay. Probably the bug was once because of #161