Fixed #25135 -- Deprecated the contrib.admin allow_tags attribute.

Thanks Jaap Roes for the idea and initial patch.

tests/admin_views/admin.py

@@ -18,6 +18,7 @@ from django.core.mail import EmailMessage
 from django.db import models
 from django.forms.models import BaseModelFormSet
 from django.http import HttpResponse, StreamingHttpResponse
+from django.utils.html import format_html
 from django.utils.safestring import mark_safe
 from django.utils.six import StringIO
 
@@ -429,7 +430,8 @@ class PostAdmin(admin.ModelAdmin):
     list_display = ['title', 'public']
     readonly_fields = (
         'posted', 'awesomeness_level', 'coolness', 'value',
-        'multiline', 'multiline_html', lambda obj: "foo"
+        'multiline', 'multiline_html', lambda obj: "foo",
+        'multiline_html_allow_tags',
     )
 
     inlines = [
@@ -444,15 +446,17 @@ class PostAdmin(admin.ModelAdmin):
 
     def value(self, instance):
         return 1000
+    value.short_description = 'Value in $US'
 
     def multiline(self, instance):
         return "Multiline\ntest\nstring"
 
     def multiline_html(self, instance):
         return mark_safe("Multiline<br>\nhtml<br>\ncontent")
-    multiline_html.allow_tags = True
 
-    value.short_description = 'Value in $US'
+    def multiline_html_allow_tags(self, instance):
+        return "Multiline<br>html<br>content<br>with allow tags"
+    multiline_html_allow_tags.allow_tags = True
 
 
 class FieldOverridePostForm(forms.ModelForm):
@@ -574,8 +578,7 @@ class ComplexSortedPersonAdmin(admin.ModelAdmin):
     ordering = ('name',)
 
     def colored_name(self, obj):
-        return '<span style="color: #%s;">%s</span>' % ('ff00ff', obj.name)
-    colored_name.allow_tags = True
+        return format_html('<span style="color: #ff00ff;">{}</span>', obj.name)
     colored_name.admin_order_field = 'name'