Fixed #12693 -- Improved error handling when there is an error setting up the database router chain. Thanks to dhageman for the report and fix.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@12305 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/utils.py

@@ -92,9 +92,14 @@ class ConnectionRouter(object):
         self.routers = []
         for r in routers:
             if isinstance(r, basestring):
+                try:
                     module_name, klass_name = r.rsplit('.', 1)
                     module = import_module(module_name)
                     router = getattr(module, klass_name)()
+                except ImportError, e:
+                    raise ImproperlyConfigured('Error importing database router %s: "%s"' % (klass_name, e))
+                except AttributeError:
+                    raise ImproperlyConfigured('Module "%s" does not define a "%s" database router' % (module, klass_name))
             else:
                 router = r
             self.routers.append(router)