Index: django/db/models/loading.py
===================================================================
--- django/db/models/loading.py	(revision 11724)
+++ django/db/models/loading.py	(working copy)
@@ -8,10 +8,37 @@
 import sys
 import os
 import threading
+import imp
+import traceback
 
 __all__ = ('get_apps', 'get_app', 'get_models', 'get_model', 'register_models',
         'load_app', 'app_cache_ready')
 
+def module_exists(full_name,path=None):
+    """
+    tests whether the module exists but does not import it.
+    see http://www.python.org/doc/current/library/imp.html#module-imp
+    """
+    a = full_name.split('.',1)
+    if len(a) == 1:
+        # simple module name without package
+        try:
+            (file, pathname, description) = imp.find_module(full_name,path)
+            if file is not None: file.close()
+        except ImportError,e:
+            return False
+        return True
+    assert len(a) == 2
+    (file, pathname, description) = imp.find_module(a[0],path)
+    if description[-1] != imp.PKG_DIRECTORY:
+        return False
+    pkg = imp.load_module(a[0],file,pathname,description)
+    if file is not None: file.close()
+    return module_exists(a[1],pkg.__path__)
+
+
+
+
 class AppCache(object):
     """
     A cache that stores installed applications and their models. Used to
@@ -57,30 +84,45 @@
                     continue
                 self.load_app(app_name, True)
             if not self.nesting_level:
-                for app_name in self.postponed:
+                postponed = self.postponed
+                self.postponed = []
+                for app_name,tb in postponed:
                     self.load_app(app_name)
                 self.loaded = True
+            if len(self.postponed):
+                msg = ''.join(["%s:\n%s" % i for i in self.postponed])
+                raise ImproperlyConfigured(
+                    "Failed to import %d applications:\n%s" % (
+                        len(self.postponed),msg))
         finally:
             self.write_lock.release()
-
+            
     def load_app(self, app_name, can_postpone=False):
         """
         Loads the app with the provided fully qualified name, and returns the
         model module.
         """
         self.handled[app_name] = None
+        if not module_exists(app_name + ".models"):
+            # silently ignore applications without models
+            #print "[DEBUG] application %s has no models" % app_name
+            return None
         self.nesting_level += 1
         try:
             models = import_module('.models', app_name)
-        except ImportError:
+        except ImportError,e:
             self.nesting_level -= 1
+            self.postponed.append( (app_name,traceback.format_exc(e)) )
             if can_postpone:
-                # Either the app has no models, or the package is still being
+                # The package is maybe still being
                 # imported by Python and the model module isn't available yet.
                 # We will check again once all the recursion has finished (in
                 # populate).
-                self.postponed.append(app_name)
-            return None
+                #print "[DEBUG] Postponing application %s:" % app_name
+                #traceback.print_exc(e)
+                return None
+            traceback.print_exc(e)
+            raise
         self.nesting_level -= 1
         if models not in self.app_store:
             self.app_store[models] = len(self.app_store)