anchor.diff:  Field object_set is not optional
   ```
   
  -This error may occur when global CPI configuration references a cluster name (via `clusters` key) that cannot be found in the datacenter. Double check in vSphere that cluster exists.
  +This error may occur when global CPI configuration references:
  +
  +- cluster (via `clusters` key) that cannot be found in the datacenter
  +- stemcell that cannot be found in the templates folder
  
positive.code: 
      datastore_pattern: '\Aprod-ds\z'
      persistent_datastore_pattern: '\Aprod-ds\z'
      allow_mixed_datastores: true
  
      clusters: [BOSH_CL]
  ```
  
negative.code: 
      datastore_pattern: '\Aprod-ds\z'
      persistent_datastore_pattern: '\Aprod-ds\z'
  
      clusters:
      - BOSH_CL: {resource_pool: BOSH_RP}
  