Merge remote-tracking branch 'origin/master' into exercise-anomaly-detection

# Conflicts:
#	Gemfile.lock

app/controllers/submissions_controller.rb

@@ -75,6 +75,11 @@ class SubmissionsController < ApplicationController
         zio.write(file.content)
       end
 
+      # zip exercise description
+      zio.put_next_entry(t('activerecord.models.exercise.one') + '.txt')
+      zio.write(@submission.exercise.title + "\r\n======================\r\n")
+      zio.write(@submission.exercise.description)
+
       # zip .co file
       zio.put_next_entry(".co")
       zio.write(File.read id_file)
@@ -167,7 +172,7 @@ class SubmissionsController < ApplicationController
           # if the command is 'client_kill', send it to docker otherwise.
           begin
             parsed = JSON.parse(data)
-            if parsed['cmd'] == 'client_kill'
+            if parsed.class == Hash && parsed['cmd'] == 'client_kill'
               Rails.logger.debug("Client exited container.")
               @docker_client.kill_container(result[:container])
             else