old_contents: try:
      from urllib.parse import urlencode
  except ImportError:
      from urllib import urlencode
  from django import template
  from django.template.defaultfilters import stringfilter
  from django.utils.html import conditional_escape
  from django.utils.safestring import mark_safe
  
  register = template.Library()
  
  
  @register.filter
  @stringfilter
  def qrcode(value, alt=None):
      url = conditional_escape("http://chart.apis.google.com/chart?%s" %
                               urlencode({'chs': '150x150', 'cht': 'qr', 'chl': value, 'choe': 'UTF-8'}))
      alt = conditional_escape(alt or value)
  
      return mark_safe(u"""<img class="qrcode" src="%s" width="150" height="150" alt="%s" />""" % (url, alt))
  
new_contents: try:
      from urllib.parse import urlencode
  except ImportError:
      from urllib import urlencode
  from django import template
  from django.template.defaultfilters import stringfilter
  from django.utils.html import conditional_escape, format_html
  
  register = template.Library()
  
  
  @register.filter
  @stringfilter
  def qrcode(value, alt=None):
      url = conditional_escape("http://chart.apis.google.com/chart?%s" %
                               urlencode({'chs': '150x150', 'cht': 'qr', 'chl': value, 'choe': 'UTF-8'}))
      alt = conditional_escape(alt or value)
  
      return format_html(u"""<img class="qrcode" src="%s" width="150" height="150" alt="%s" />""" % (url, alt))
  
subject: Remove use of `mark_safe`