add buildpack name to unready validation failure message

[#173038631]

Co-authored-by: Matt Royal <mroyal@pivotal.io>
Co-authored-by: Connor Braa <cbraa@pivotal.io>

Author: matt-royal

app/models/runtime/app_model.rb

@@ -169,7 +169,7 @@ def validate_buildpacks_are_ready
           buildpack = Buildpack.find(name: blb.admin_buildpack_name)
 
           if buildpack && buildpack.state != Buildpack::READY_STATE
-            errors.add(:buildpack, 'must be in ready state')
+            errors.add(:buildpack, "#{buildpack.name.inspect} must be in ready state")
           end
         end
       end

spec/unit/models/runtime/app_model_spec.rb

@@ -267,14 +267,14 @@ module VCAP::CloudController
 
       describe 'buildpacks' do
         let(:ready_buildpack) { Buildpack.make(filename: 'some-file') }
-        let(:unready_buildpack) { Buildpack.make(filename: nil) }
+        let(:unready_buildpack) { Buildpack.make(name: 'unready', filename: nil) }
         let!(:buildpack_lifecycle_data) { BuildpackLifecycleDataModel.make(app: app_model, buildpacks: [ready_buildpack.name, unready_buildpack.name]) }
 
         it 'does not allow buildpacks that are not READY' do
           expect {
             app_model.buildpack_lifecycle_data = buildpack_lifecycle_data
             app_model.save
-          }.to raise_error(Sequel::ValidationFailed, /must be in ready state/)
+          }.to raise_error(Sequel::ValidationFailed, /"unready" must be in ready state/)
         end
 
         it 'is valid with buildpacks that are READY' do