More precisely identify Django loaders.

coffin/template/loaders.py

@@ -9,6 +9,8 @@ def jinja_loader_from_django_loader(django_loader):
     :return: The similarly-behaving Jinja loader, or None if a similar loader
         could not be found.
     """
+    if not django_loader.startswith('django.'):
+        return None
     for substr, func in _JINJA_LOADER_BY_DJANGO_SUBSTR.iteritems():
         if substr in django_loader:
             return func()

tests/test_env.py

@@ -9,3 +9,17 @@
 def test_i18n():
     with override_settings(USE_I18N=True):
         assert get_env().from_string('{{ _("test") }}').render() == 'test'
+
+
+def test_django_loader_replace():
+    from coffin.template.loaders import jinja_loader_from_django_loader
+    from jinja2 import loaders
+
+    # Test replacement of filesystem loader
+    l = jinja_loader_from_django_loader('django.template.loaders.filesystem.Loader')
+    assert isinstance(l, loaders.FileSystemLoader)
+
+    # Since we don't do exact matches for the loader string, make sure we
+    # are not replacing loaders that are outside the Django namespace.
+    l = jinja_loader_from_django_loader('djangoaddon.template.loaders.filesystem.Loader')
+    assert not isinstance(l, loaders.FileSystemLoader)