Make box_url optional

[ashb]

Vagrant 1.5 doesn’t need it anymore, just the name from the Vagrant cloud

[ashb]

This seems to be failing it's tests with this error NameError: uninitialized constant LogSwitch::Mixin which appears to be caused by one of our down stream deps, Tailor: turboladen/tailor#160

[sethvargo]

Seems reasonable to me 👍

[legal90]

Yes, we need this too 👍
We are using our boxes for parallels provider and it fails if there is only "box" specified in kitchen.yml:

# kitchen.yml
...
platforms:
  - name: debian-7.6
    driver:
      provider: parallels
      box: parallels/debian-7.6

# Kitchen output
...
           default: Downloading: https://opscode-vm-bento.s3.amazonaws.com/vagrant/parallels/opscode_debian-7.6_chef-provisionerless.box
>>>>>> ------Exception-------
>>>>>> Class: Kitchen::ActionFailed
>>>>>> Message: Failed to complete #create action: [Expected process to exit with [0], but received '1'
---- Begin output of vagrant up --no-provision --provider=parallels ----
STDOUT: Bringing machine 'default' up with 'parallels' provider...
==> default: Box 'parallels/debian-7.6' could not be found. Attempting to find and install...
    default: Box Provider: parallels
    default: Box Version: >= 0
==> default: Adding box 'parallels/debian-7.6' (v0) for provider: parallels
    default: Downloading: https://opscode-vm-bento.s3.amazonaws.com/vagrant/parallels/opscode_debian-7.6_chef-provisionerless.box
...

So, I guess this pull request will fix that.

[sethvargo]

Merged in 63f9eef. Thanks!

[fnichol]

I've slightly changed the semantics of this PR in #151 but I'm hopeful that the end result is very similar. The description should help explain the rationale, but now if you want to reference base boxes on Atlas, there's less configuration getting in your way.

@legal90, I took a spin with your example above and confirmed that :box_url won't be set--actually it should never be set by default for the Parallels provider as there aren't currently any hosted Parallels Bento base boxes on S3. In other words, I'm very hopeful that your .kitchen.yml files will be much less impacted 😄