Django 1.11: Remove jinja2 backend.

Django 1.11 adds the ability to pass context processors in Jinja2
backend. Django also sends template_rendered signal in tests.
These two issues were the reason why we added Jinja2 backend, but
after upgrading to Django 1.11 we can remove it.

We still need jinja2/__init__.py, which modifies the environment,
and jinja2/compressors.py, which adds minify_js compressor.

zproject/jinja2/backends.py

@@ -1,97 +0,0 @@
-from __future__ import absolute_import
-
-import six
-import sys
-
-from typing import Any, Dict, List, Optional, Union, Text
-if False:
-    from mypy_extensions import NoReturn
-
-import jinja2
-from django.test.signals import template_rendered
-from django.template.backends import jinja2 as django_jinja2
-from django.template import TemplateDoesNotExist, TemplateSyntaxError, Context
-from django.http import HttpRequest
-
-
-class Jinja2(django_jinja2.Jinja2):
-    """Context processors aware Jinja2 backend.
-
-    The default Jinja2 backend in Django is not aware of context
-    processors so we just derive from the default Jinja2 backend
-    and add the functionality to pass the context processors to
-    the `Template` object.
-    """
-
-    def __init__(self, params, *args, **kwargs):
-        # type: (Dict[str, Any], *Any, **Any) -> None
-        # We need to remove `context_processors` from `OPTIONS` because
-        # `Environment` doesn't expect it
-        context_processors = params['OPTIONS'].pop('context_processors', [])
-        debug = params['OPTIONS'].pop('debug', False)
-        super(Jinja2, self).__init__(params, *args, **kwargs)
-
-        # We need to create these two properties after calling the __init__
-        # of base class so that they are not overridden.
-        self.context_processors = context_processors
-        self.debug = debug
-
-    def get_template(self, template_name):
-        # type: (str) -> Template
-        """
-        The only we need to override this function is to use our own Template
-        class. Jinja2 backend doesn't allow the usage of custom Template
-        class.
-
-        If in the future Django adds a method through which we can get a
-        custom Template class, this method can be safely removed.
-        """
-        try:
-            return Template(self.env.get_template(template_name), self)
-        except jinja2.TemplateNotFound as exc:
-            six.reraise(TemplateDoesNotExist, TemplateDoesNotExist(exc.args),
-                        sys.exc_info()[2])
-        except jinja2.TemplateSyntaxError as exc:
-            six.reraise(TemplateSyntaxError, TemplateSyntaxError(exc.args),
-                        sys.exc_info()[2])
-
-    def from_string(self, template_code):
-        # type: (str) -> Template
-        """
-        The only need to override this function is to use our own Template
-        class. Jinja2 backend doesn't allow the usage of custom Template
-        class.
-
-        If in the future Django adds a method through which we can get a
-        custom Template class, this method can be safely removed.
-        """
-        return Template(self.env.from_string(template_code), self)
-
-
-class Template(django_jinja2.Template):
-        """
-        We need this class so that we can send the template_rendered signal,
-        and to flatten the context if it is an instance of Context class.
-        """
-        def render(self, context=None, request=None):
-            # type: (Optional[Union[Dict[str, Any], Context]], Optional[HttpRequest]) -> Text
-            if context is None:
-                context = {}
-
-            if isinstance(context, Context):
-                # Jinja2 expects a dictionary
-                # This condition makes sure that `flatten` is called only when
-                # `context` is an instance of `Context`.
-                #
-                # Note: If we don't ignore then mypy complains about missing
-                # `flatten` attribute in some members of union.
-                context = context.flatten()  # type: ignore
-
-            result = super(Template, self).render(context=context,
-                                                  request=request)
-
-            if self.backend.debug:
-                template_rendered.send(sender=self, template=self,
-                                       context=context)
-
-            return result

zproject/settings.py

@@ -296,9 +296,8 @@ if PRODUCTION:
     LOADERS = [('django.template.loaders.cached.Loader', LOADERS)]
 
 base_template_engine_settings = {
-    'BACKEND': 'zproject.jinja2.backends.Jinja2',
+    'BACKEND': 'django.template.backends.jinja2.Jinja2',
     'OPTIONS': {
-        'debug': DEBUG,
         'environment': 'zproject.jinja2.environment',
         'extensions': [
             'jinja2.ext.i18n',