old_contents: from django.core.exceptions import ValidationError
  import re
  
  
  mac_match = "^[0-9a-f]{12}$"
  is_mac = re.compile(mac_match)
  
  MAC_ERR = "Mac Address not of valid type."
  EMPTY_MAC_ERR = "If you want to use a blank mac address, uncheck Dhcp enabled"
  
  def validate_mac(mac):
      if not isinstance(mac, basestring) or not is_mac.match(mac):
          raise ValidationError(MAC_ERR)
      if mac == '000000000000':
          raise ValidationError(EMPTY_MAC_ERR)
  
new_contents: from django.core.exceptions import ValidationError
  import re
  
  
  mac_match = "^[0-9a-f]{12}$"
  is_mac = re.compile(mac_match)
  
  MAC_ERR = "MAC address not of valid type."
  EMPTY_MAC_ERR = ('If you want to use a blank MAC address, uncheck "DHCP '
                   'enabled"')
  
  def validate_mac(mac):
      if not isinstance(mac, basestring) or not is_mac.match(mac):
          raise ValidationError(MAC_ERR)
      if mac == '000000000000':
          raise ValidationError(EMPTY_MAC_ERR)
  
subject: Fix some capitalization issues