[1.9.x] Fixed #25466 -- Added backwards compatibility aliases for LoaderOrigin and StringOrigin.

Thanks Simon Charette for the DeprecationInstanceCheck class.

Backport of 8d1a001ef6 from master

django/template/__init__.py

@@ -58,7 +58,8 @@ from .exceptions import TemplateDoesNotExist, TemplateSyntaxError       # NOQA i
 
 # Template parts
 from .base import (                                                     # NOQA isort:skip
-    Context, Node, NodeList, Origin, RequestContext, Template, Variable,
+    Context, Node, NodeList, Origin, RequestContext, StringOrigin, Template,
+    Variable,
 )
 
 # Deprecated in Django 1.8, will be removed in Django 1.10.

django/template/base.py

@@ -60,7 +60,10 @@ from django.template.context import (  # NOQA: imported for backwards compatibil
     BaseContext, Context, ContextPopException, RequestContext,
 )
 from django.utils import six
-from django.utils.deprecation import RemovedInDjango110Warning
+from django.utils.deprecation import (
+    DeprecationInstanceCheck, RemovedInDjango20Warning,
+    RemovedInDjango110Warning,
+)
 from django.utils.encoding import (
     force_str, force_text, python_2_unicode_compatible,
 )
@@ -158,6 +161,11 @@ class Origin(object):
             )
 
 
+class StringOrigin(six.with_metaclass(DeprecationInstanceCheck, Origin)):
+    alternative = 'django.template.Origin'
+    deprecation_warning = RemovedInDjango20Warning
+
+
 class Template(object):
     def __init__(self, template_string, origin=None, name=None, engine=None):
         try:

django/template/loader.py

@@ -1,9 +1,14 @@
 import warnings
 
-from django.utils.deprecation import RemovedInDjango110Warning
+from django.utils import six
+from django.utils.deprecation import (
+    DeprecationInstanceCheck, RemovedInDjango20Warning,
+    RemovedInDjango110Warning,
+)
 
 from . import engines
 from .backends.django import DjangoTemplates
+from .base import Origin
 from .engine import (
     _context_instance_undefined, _dictionary_undefined, _dirs_undefined,
 )
@@ -147,3 +152,8 @@ class BaseLoader(base.Loader):
             "django.template.loaders.base.Loader.",
             RemovedInDjango110Warning, stacklevel=2)
         super(BaseLoader, self).__init__(*args, **kwargs)
+
+
+class LoaderOrigin(six.with_metaclass(DeprecationInstanceCheck, Origin)):
+    alternative = 'django.template.Origin'
+    deprecation_warning = RemovedInDjango20Warning