Some comments and cleanup of exercise.rb percentage calculation

lib/docker_client.rb

@@ -96,8 +96,9 @@ class DockerClient
     #Rails.logger.info "docker_client: self.create_container with creation options:"
     #Rails.logger.info(container_creation_options(execution_environment))
     container = Docker::Container.create(container_creation_options(execution_environment))
+    # container.start sometimes creates the passed local_workspace_path on disk (depending on the setup).
+    # this is however not guaranteed and caused issues on the server already. Therefore create the necessary folders manually!
     local_workspace_path = generate_local_workspace_path
-    # container.start always creates the passed local_workspace_path on disk. Seems like we have to live with that, therefore we can also just create the empty folder ourselves.
     FileUtils.mkdir(local_workspace_path)
     container.start(container_start_options(execution_environment, local_workspace_path))
     container.start_time = Time.now

lib/docker_container_pool.rb

@@ -48,6 +48,7 @@ class DockerContainerPool
   end
 
   def self.create_container(execution_environment)
+    Rails.logger.info('trying to create container for execution environment: ' + execution_environment.to_s)
     container = DockerClient.create_container(execution_environment)
     container.status = 'available'
     #Rails.logger.debug('created container ' + container.to_s + ' for execution environment ' + execution_environment.to_s)