Fix django 2.0 compatibility

Author: EternalSoul

Diff for: .gitignore

@@ -7,3 +7,4 @@ MANIFEST
 *egg*
 *.bak
 *.tmproj
+.idea

Diff for: genericadmin/admin.py

@@ -23,6 +23,7 @@
 except ImportError:
     from django.contrib.admin.options import IS_POPUP_VAR
 from  django.core.exceptions import ObjectDoesNotExist
+from django.views.generic import RedirectView
 
 JS_PATH = getattr(settings, 'GENERICADMIN_JS', 'genericadmin/js/')
 
@@ -63,7 +64,12 @@ def get_generic_field_list(self, request, prefix=''):
                     fields['prefix'] = prefix
                     field_list.append(fields)
         else:
-            for field in self.model._meta.virtual_fields:
+            # virtual_fields were deprecated in django 2.0
+            try:
+                fields = self.model._meta.virtual_fields
+            except AttributeError:
+                fields = self.model._meta.private_fields
+            for field in fields:
                 if isinstance(field, GenericForeignKey) and \
                         field.ct_field not in exclude and field.fk_field not in exclude:
                     field_list.append({
@@ -90,6 +96,10 @@ def wrapper(*args, **kwargs):
         custom_urls = [
             url(r'^obj-data/$', wrap(self.generic_lookup), name='admin_genericadmin_obj_lookup'),
             url(r'^genericadmin-init/$', wrap(self.genericadmin_js_init), name='admin_genericadmin_init'),
+
+            # to work with django 2.0
+            url(r'../genericadmin-init/change/$',
+                wrap(RedirectView.as_view(pattern_name='%s:admin_genericadmin_init' % self.admin_site.name))),
         ]
         return custom_urls + super(BaseGenericModelAdmin, self).get_urls()