We now check for powershell/dsc compat in provider.
The problem with raising an exception when the resource is created
was that it was not possible to have a chef recipe that installs
the correct version of powershell and then runs the dsc_script
resource.
See https://github.com/opscode/chef/issues/2027
Merge pull request #2103 from opscode/jdmundrawala/issue-2027-master

We now check for powershell/dsc compat in provider.