Accommodate Django 1.8's template system changes

Django 1.8 introduces the possibility of using multiple template
engines, which means that some components of Django's template system
have been encapsulated in an Engine class instead of being available
globally, and other parts refactored and moved around.

mezzanine/core/templatetags/mezzanine_tags.py

@@ -14,10 +14,19 @@
 from django.core.files import File
 from django.core.files.storage import default_storage
 from django.core.urlresolvers import reverse, resolve, NoReverseMatch
-from django.template import (Context, Node, TextNode, Template,
-    TemplateSyntaxError, TOKEN_TEXT, TOKEN_VAR, TOKEN_COMMENT, TOKEN_BLOCK)
 from django.db.models import Model
 from django.db.models.loading import get_model
+from django.template import Context, Node, Template, TemplateSyntaxError
+
+try:
+    # Django >= 1.8
+    from django.template.base import (TOKEN_BLOCK, TOKEN_COMMENT,
+                                      TOKEN_TEXT, TOKEN_VAR, TextNode)
+except ImportError:
+    # Django <= 1.7
+    from django.template import (TOKEN_BLOCK, TOKEN_COMMENT,
+                                 TOKEN_TEXT, TOKEN_VAR, TextNode)
+
 from django.template.defaultfilters import escape
 from django.template.loader import get_template
 from django.utils import translation

mezzanine/template/__init__.py

@@ -110,15 +110,16 @@ def render(self, context):
                             else:
                                 ts = templates_for_device(request, name)
                                 t = select_template(ts)
-                            self.nodelist = t.nodelist
+
+                            self.template = t
                         parts = [template.Variable(part).resolve(context)
                                  for part in token.split_contents()[1:]]
                         if takes_context:
                             parts.insert(0, context)
                         result = tag_func(*parts)
                         autoescape = context.autoescape
                         context = context_class(result, autoescape=autoescape)
-                        return self.nodelist.render(context)
+                        return self.template.render(context)
 
                 return InclusionTagNode()
             return self.tag(tag_wrapper)

mezzanine/template/loader_tags.py

@@ -5,7 +5,6 @@
 
 from django.template import Template, TemplateSyntaxError, TemplateDoesNotExist
 from django.template.loader_tags import ExtendsNode
-from django.template.loader import find_template_loader
 
 from mezzanine import template
 
@@ -47,7 +46,21 @@ def find_template(self, name, context, peeking=False):
 
         # These imports want settings, which aren't available when this
         # module is imported to ``add_to_builtins``, so do them here.
-        from django.template.loaders.app_directories import app_template_dirs
+        import django.template.loaders.app_directories as app_directories
+        try:
+            # Django >= 1.8
+            app_template_dirs = app_directories.get_app_template_dirs
+        except AttributeError:
+            # Django <= 1.7
+            app_template_dirs = app_directories.app_template_dirs
+
+        try:
+            # Django >= 1.8
+            find_template_loader = context.engine.find_template_loader
+        except AttributeError:
+            # Django <= 1.7
+            from django.template.loaders import find_template_loader
+
         from mezzanine.conf import settings
 
         # Store a dictionary in the template context mapping template