[soc2009/multidb] Raise a ConnectionDoesNotExist exception, instead of a KeyError for an invaid connection

git-svn-id: http://code.djangoproject.com/svn/django/branches/soc2009/multidb@11424 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/utils.py

@@ -32,6 +32,8 @@ def load_backend(backend_name):
             else:
                 raise # If there's some other error, this must be an error in Django itself.
 
+class ConnectionDoesNotExist(Exception):
+    pass
 
 class ConnectionHandler(object):
     def __init__(self, databases):
@@ -43,7 +45,10 @@ class ConnectionHandler(object):
         Puts the defaults into the settings dictionary for a given connection
         where no settings is provided.
         """
+        try:
             conn = self.databases[alias]
+        except KeyError:
+            raise ConnectionDoesNotExist("The connection %s doesn't exist" % alias)
         conn.setdefault('DATABASE_ENGINE', 'dummy')
         conn.setdefault('DATABASE_OPTIONS', {})
         conn.setdefault('TEST_DATABASE_CHARSET', None)

docs/topics/db/multi-db.txt

@@ -23,7 +23,9 @@ settings for that specific connection.  The settings in the inner dictionaries
 are described fully in the :settings:`DATABASES` documentation.  The important
 thing to note is that your primary database should have the alias
 ``'default'``, and any additional databases you have can have whatever alias
-you choose.
+you choose.  If at any time you attempt to access a database that isn't defined
+in your :settings:`DATABASES` setting then Django will raise a
+``django.db.utils.ConnectionDoesNotExist`` exception.
 
 Selecting a Database for a ``Model``
 ====================================
@@ -62,4 +64,4 @@ keyword argument to ``save()``.  For example if you were migrating a user from
 the ``'legacy_users'`` database to the ``'new_users'`` database you might do::
 
     >>> user_obj.save(using='new_users')
-    >>> usre_obj.delete(using='legacy_users')
+    >>> user_obj.delete(using='legacy_users')