Azure errors are not wrapped correctly

[ShimShtein]

In cases when Azure throws an error, for example if credentials are wrong on while testing a connection, instead of the original error, NoMethodError (undefined method []' for nil:NilClass)` error is thrown.

This comes from fog-azure-rm-downgraded-0.3.1/lib/fog/azurerm/utilities/general.rb @ line 51 Object#raise_azure_exception. The original exception looks like this:

[6] pry(#<Fog::Resources::AzureRM::Real>)> exception
=> #<MsRestAzure::AzureOperationError: {
  "message": "Couldn't login to Azure, please verify your tenant id, client id and client secret",
  "request": null,
  "response": null
}>

But body property is nil.