Fix MongoClient.__getattr__ implementation.

Before, MongoClient._does_not_exist had raised AttributeError, 'super' object has no
attribute '__getattr__'. Now it raises, AttributeError: MongoClient has no attribute
'_does_not_exist'. To access the _does_not_exist database, use client['_does_not_exist'].

pymongo/collection.py

@@ -154,7 +154,11 @@ class Collection(common.BaseObject):
           - `name`: the name of the collection to get
         """
         if name.startswith('_'):
-            return super(Collection, self).__getattr__(name)
+            full_name = '%s.%s' % (self.__name, name)
+            raise AttributeError(
+                "Collection has no attribute %r. To access the %s"
+                " collection, use database['%s']." % (
+                    name, full_name, full_name))
         return self.__getitem__(name)
 
     def __getitem__(self, name):

pymongo/database.py

@@ -209,7 +209,9 @@ class Database(common.BaseObject):
           - `name`: the name of the collection to get
         """
         if name.startswith('_'):
-            return super(Database, self).__getattr__(name)
+            raise AttributeError(
+                "Database has no attribute %r. To access the %s"
+                " collection, use database[%r]." % (name, name, name))
         return self.__getitem__(name)
 
     def __getitem__(self, name):

pymongo/mongo_client.py

@@ -946,7 +946,9 @@ class MongoClient(common.BaseObject):
           - `name`: the name of the database to get
         """
         if name.startswith('_'):
-            return super(MongoClient, self).__getattr__(name)
+            raise AttributeError(
+                "MongoClient has no attribute %r. To access the %s"
+                " database, use client[%r]." % (name, name, name))
         return self.__getitem__(name)
 
     def __getitem__(self, name):

test/test_client.py

@@ -136,9 +136,15 @@ class ClientUnitTest(unittest.TestCase, TestRequestMixin):
     def test_getattr(self):
         self.assertTrue(isinstance(self.client['_does_not_exist'], Database))
 
-        with self.assertRaises(AttributeError):
+        with self.assertRaises(AttributeError) as context:
             self.client._does_not_exist
 
+        # Message should be:
+        # "AttributeError: MongoClient has no attribute '_does_not_exist'. To
+        # access the _does_not_exist database, use client['_does_not_exist']".
+        self.assertIn("has no attribute '_does_not_exist'",
+                      str(context.exception))
+
     def test_iteration(self):
         def iterate():
             [a for a in self.client]

test/test_collection.py

@@ -90,9 +90,16 @@ class TestCollectionNoConnect(unittest.TestCase):
         coll = self.db.test
         self.assertTrue(isinstance(coll['_does_not_exist'], Collection))
 
-        with self.assertRaises(AttributeError):
+        with self.assertRaises(AttributeError) as context:
             coll._does_not_exist
 
+        # Message should be:
+        # "AttributeError: Collection has no attribute '_does_not_exist'. To
+        # access the test._does_not_exist collection, use
+        # database['test._does_not_exist']."
+        self.assertIn("has no attribute '_does_not_exist'",
+                      str(context.exception))
+
     def test_iteration(self):
         self.assertRaises(TypeError, next, self.db)
 

test/test_database.py

@@ -94,9 +94,15 @@ class TestDatabaseNoConnect(unittest.TestCase):
         db = self.client.pymongo_test
         self.assertTrue(isinstance(db['_does_not_exist'], Collection))
 
-        with self.assertRaises(AttributeError):
+        with self.assertRaises(AttributeError) as context:
             db._does_not_exist
 
+        # Message should be: "AttributeError: Database has no attribute
+        # '_does_not_exist'. To access the _does_not_exist collection,
+        # use database['_does_not_exist']".
+        self.assertIn("has no attribute '_does_not_exist'",
+                      str(context.exception))
+
     def test_iteration(self):
         self.assertRaises(TypeError, next, self.client.pymongo_test)