Provide error handling for when the directory can't be deleted

app/controllers/workspaces_controller.rb

@@ -23,6 +23,8 @@ def destroy
     head :no_content
   rescue Errno::ENOENT => e
     render build_error('Unable to remove directory', e)
+  rescue Errno::ENOTEMPTY => e
+    render build_error('Unable to remove directory', e)
   end
 
   # Once an object has been transferred to preservation clean up the workspace.

app/services/cleanup_service.rb

@@ -13,6 +13,7 @@ def self.cleanup_by_druid(druid)
   # @param [String] druid The identifier for the object whose data is to be removed
   # @param [String] base The base directory to delete from
   # @return [void] remove the object's data files from the workspace area
+  # @raises [Errno::ENOTEMPTY] if the directory is not empty
   def self.cleanup_workspace_content(druid, base)
     PruneService.new(druid: DruidTools::Druid.new(druid, base)).prune!
   end

app/services/prune_service.rb

@@ -7,6 +7,7 @@ def initialize(druid:)
     @druid = druid
   end
 
+  # @raises [Errno::ENOTEMPTY] if the directory is not empty
   def prune!
     this_path = druid.pathname
     parent = this_path.parent

spec/requests/cleanup_workspace_spec.rb

@@ -18,7 +18,7 @@
     end
   end
 
-  context 'when an error is raised' do
+  context "when the directory doesn't exist" do
     before do
       allow(CleanupService).to receive(:cleanup_by_druid)
         .and_raise(Errno::ENOENT, 'dir_s_rmdir - /dor/workspace/aa/222')
@@ -34,4 +34,21 @@
       )
     end
   end
+
+  context 'when the directory is not empty' do
+    before do
+      allow(CleanupService).to receive(:cleanup_by_druid)
+        .and_raise(Errno::ENOTEMPTY, 'dir_s_rmdir - /dor/assembly/pw/569/pw/4290')
+    end
+
+    it 'returns JSON-API error' do
+      delete "/v1/objects/#{object_id}/workspace",
+             headers: { 'Authorization' => "Bearer #{jwt}" }
+      expect(response).to have_http_status(:unprocessable_entity)
+      expect(response.body).to eq(
+        '{"errors":[{"status":"422","title":"Unable to remove directory",' \
+        '"detail":"Directory not empty - dir_s_rmdir - /dor/assembly/pw/569/pw/4290"}]}'
+      )
+    end
+  end
 end