old_contents: import re
  from django.core.validators import RegexValidator
  from django.utils.translation import ugettext_lazy as _
  
  name_re = re.compile(r'^[a-zA-Z0-9]([-a-zA-Z0-9_.]*[a-zA-Z0-9])?$')
  name_re = re.compile(r'^[a-zA-Z0-9]+$')
  validate_name = RegexValidator(name_re, _("Enter a valid name consisting of letters, numbers, underscores, hyphens or dots."), 'invalid')
  
  
new_contents: import re
  from django.core.validators import RegexValidator
  from django.utils.translation import ugettext_lazy as _
  
  name_re = re.compile(r'^[a-zA-Z0-9][a-zA-Z0-9_.+-]*$')
  validate_name = RegexValidator(name_re, _('Enter a valid name consisting of letters, numbers, underscores, hyphens, pluses or dots.'), 'invalid')
  
  
subject: allow + in the name