old_contents: import time
  import uuid
  import shutil
  
  from django.db import models
  from django.template.defaultfilters import filesizeformat
  from django.contrib.auth.models import User
  from django.utils import timezone
  from django.utils.translation import ugettext_lazy as _
  
  import forms
  
  
  DB_NAME_LENGTH = 100
  
  
  class Team(models.Model):
      id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
      name = models.CharField(max_length=DB_NAME_LENGTH)
      user = models.ForeignKey(User)
      passed = models.BooleanField()
      avatar = models.ImageField(upload_to='avatars', null=True, blank=True)
  
      def __unicode__(self):
          return self.name
  
  
  def submission_directory_path(instance, filename):
      # file will be uploaded to MEDIA_ROOT/submissions/<id>/<filename>
      return 'submissions/{0}/{1}'.format(instance.id, filename)
  
  
  class Submission(models.Model):
      id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
      team = models.ForeignKey(Team)
      user = models.ForeignKey(User)
      date = models.DateTimeField(default=timezone.now)
      package = models.FileField(
          upload_to=submission_directory_path,
          blank=True,
          null=True
      )
      # User-specified command for code execution
      command = models.CharField(max_length=1000)
  
      def __unicode__(self):
          return unicode(self.date) + ' ' + unicode(self.id) + \
              ' - submitted by: ' + unicode(self.team)
  
      def delete(self, *args, **kwargs):
          for result in Result.objects.filter(submission_id__exact = self.id):
              result.delete()
          dir_path = os.path.dirname(self.package.path)
          print "Submission directory path to delete: {}".format(dir_path)
          shutil.rmtree(dir_path, ignore_errors=True)
          super(Submission, self).delete(*args, **kwargs)
  
  
  class Result(models.Model):
      id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
      submission_id = models.UUIDField(primary_key=False, default=uuid.uuid4, editable=False)
      report = models.CharField(max_length=1000, default='{}')
      log = models.CharField(max_length=10000, default='')
  
      def __unicode__(self):
          return unicode(self.id) + ' - with report: ' + unicode(self.report)
  
  
  
new_contents: import time
  import uuid
  import shutil
  import os
  
  from django.db import models
  from django.template.defaultfilters import filesizeformat
  from django.contrib.auth.models import User
  from django.utils import timezone
  from django.utils.translation import ugettext_lazy as _
  
  import forms
  
  
  DB_NAME_LENGTH = 100
  
  
  class Team(models.Model):
      id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
      name = models.CharField(max_length=DB_NAME_LENGTH)
      user = models.ForeignKey(User)
      passed = models.BooleanField()
      avatar = models.ImageField(upload_to='avatars', null=True, blank=True)
  
      def __unicode__(self):
          return self.name
  
  
  def submission_directory_path(instance, filename):
      # file will be uploaded to MEDIA_ROOT/submissions/<id>/<filename>
      return 'submissions/{0}/{1}'.format(instance.id, filename)
  
  
  class Submission(models.Model):
      id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
      team = models.ForeignKey(Team)
      user = models.ForeignKey(User)
      date = models.DateTimeField(default=timezone.now)
      package = models.FileField(
          upload_to=submission_directory_path,
          blank=True,
          null=True
      )
      # User-specified command for code execution
      command = models.CharField(max_length=1000)
  
      def __unicode__(self):
          return unicode(self.date) + ' ' + unicode(self.id) + \
              ' - submitted by: ' + unicode(self.team)
  
      def delete(self, *args, **kwargs):
          for result in Result.objects.filter(submission_id__exact = self.id):
              result.delete()
          dir_path = os.path.dirname(self.package.path)
          print "Submission directory path to delete: {}".format(dir_path)
          shutil.rmtree(dir_path, ignore_errors=True)
          super(Submission, self).delete(*args, **kwargs)
  
  
  class Result(models.Model):
      id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
      submission_id = models.UUIDField(primary_key=False, default=uuid.uuid4, editable=False)
      report = models.CharField(max_length=1000, default='{}')
      log = models.CharField(max_length=10000, default='')
  
      def __unicode__(self):
          return unicode(self.id) + ' - with report: ' + unicode(self.report)
  
  
  
subject: Add missing os import