Better logging when bad extension class is given.

This was necessary to debug an issue with different unit tests influencing
each other in Attract.

pillar/__init__.py

@@ -182,8 +182,13 @@ class PillarServer(Eve):
     def load_extension(self, pillar_extension, url_prefix):
         from .extension import PillarExtension
 
-        assert isinstance(pillar_extension, PillarExtension), \
+        if not isinstance(pillar_extension, PillarExtension):
-            'Extension has wrong type %r' % type(pillar_extension)
+            if self.config.get('DEBUG'):
+                for cls in type(pillar_extension).mro():
+                    self.log.error('class %42r (%i) is %42r (%i): %s',
+                                   cls, id(cls), PillarExtension, id(PillarExtension),
+                                   cls is PillarExtension)
+            raise AssertionError('Extension has wrong type %r' % type(pillar_extension))
         self.log.info('Loading extension %s', pillar_extension.name)
 
         # Remember this extension, and disallow duplicates.

pillar/tests/__init__.py

@@ -1,5 +1,7 @@
 # -*- encoding: utf-8 -*-
 
+from __future__ import print_function
+
 from __future__ import absolute_import
 
 import base64
@@ -94,9 +96,15 @@ class AbstractPillarTest(TestMinimal):
 
         # Not only delete self.app (like the superclass does),
         # but also un-import the application.
-        del sys.modules['pillar']
+        self.unload_modules('pillar')
-        remove = [modname for modname in sys.modules
+
-                  if modname.startswith('pillar.')]
+    def unload_modules(self, module_name):
+        """Uploads the named module, and all submodules."""
+
+        del sys.modules[module_name]
+
+        remove = {modname for modname in sys.modules
+                  if modname.startswith('%s.' % module_name)}
         for modname in remove:
             del sys.modules[modname]