Before this change, the detection of a non-existing path on the guest
machine was considered as an error and lead to interrupt the current vagrant
action. This was actually a mistake to do so, since the config checks
are performed before many other vagrant actions than `provision`.
The config.validate phase is also intended to primarily check the options
sanity, but it cannot be too strict with the guest state (which can easily
get "out of automatic control").
With this change, we still apply these checks (when possible), but only warn
about possible configuration problems. This way, the subsequent
statements will happen anyway (e.g. ansible commands will be
executed, vagrant machine will be destroyed, etc.)
With this change, the existing host-based Ansible provisioner is
refactored to share a maximum of code with this new guest-based Ansible
provisioner.
At this stage of development, the existing unit tests are intentionally
modified as little as possible, to keep safe the existing funtionalities.
Other issues resolved by this changeset:
- Display a warning when running from a Windows host [GH-5292]
- Do not run `ansible-playbook` in verbose mode when the `verbose` option
is set to an empty string.