Remove django-load dependency

This library was outdated, not supporting neither Python3 nor
Django 1.11. This patch adds the same functionality using
Django API instead.

setup.py

@@ -16,7 +16,6 @@
     'python-memcached',
     'jsonfield',
     'logutils',           # required for django-medusa
-    'django-load',
     'django-compressor',
     'django-bootstrap-form',
     'django-sekizai',

wsgi/healthmeter/importerutils/registry.py

@@ -2,9 +2,13 @@
 # License: GPLv3 or any later version
 
 import collections
+import logging
 
 from django.apps import apps
-from django_load.core import load
+from django.utils.module_loading import import_module
+
+
+logger = logging.getLogger(__name__)
 
 
 ImporterEntry = collections.namedtuple('ImporterEntry', ['cls', 'key'])
@@ -36,7 +40,6 @@ def lookup_importer(model):
         for key, value in importers_by_model.items():
             if key in model.__mro__:
                 return value
-
         raise e
 
 
@@ -53,8 +56,17 @@ def load_importer_modules():
     Import .importers for each app in INSTALLED_APPS
     """
     global _importers_loaded
+
     if _importers_loaded:
         return
 
-    load('importers')
+    for app_cfg in apps.get_app_configs():
+        module_name = '%s.%s' % (app_cfg.name, 'importers')
+
+        try:
+            import_module(module_name)
+        except ImportError:
+            logger.warning("Importing %s app importers %s module",
+                           app_cfg.name, module_name)
+
     _importers_loaded = True