LocoStudio
diff --git a/‎cassandra/cqlengine/connection.py‎
Lines changed: 1 addition & 1 deletion b/‎cassandra/cqlengine/connection.py‎
Lines changed: 1 addition & 1 deletion
diff --git a/‎cassandra/cqlengine/models.py‎
Lines changed: 8 additions & 3 deletions b/‎cassandra/cqlengine/models.py‎
Lines changed: 8 additions & 3 deletions
diff --git a/‎cassandra/cqlengine/query.py‎
Lines changed: 8 additions & 5 deletions b/‎cassandra/cqlengine/query.py‎
Lines changed: 8 additions & 5 deletions
@@ -146,7 +146,7 @@ def unregister_connection(name):
     if name not in _connections:
         return
 
-    if _connections[name] == _connections[DEFAULT_CONNECTION]:
+    if DEFAULT_CONNECTION in _connections and _connections[name] == _connections[DEFAULT_CONNECTION]:
         del _connections[DEFAULT_CONNECTION]
         log.warning("Unregistering default connection '{0}'. Use set_default_connection to set a new one.".format(name))
 
 
@@ -31,9 +31,12 @@
 
 def _clone_model_class(model, attrs):
     new_type = type(model.__name__, (model,), attrs)
-    new_type.__abstract__ = model.__abstract__
-    new_type.__discriminator_value__ = model.__discriminator_value__
-    new_type.__default_ttl__ = model.__default_ttl__
+    try:
+        new_type.__abstract__ = model.__abstract__
+        new_type.__discriminator_value__ = model.__discriminator_value__
+        new_type.__default_ttl__ = model.__default_ttl__
+    except AttributeError:
+        pass
     return new_type
 
 
@@ -803,6 +806,8 @@ def _class_batch(cls, batch):
 
     def _inst_batch(self, batch):
         assert self._timeout is connection.NOT_SET, 'Setting both timeout and batch is not supported'
+        if self._connection:
+            raise CQLEngineException("Cannot specify a connection on model in batch mode.")
         self._batch = batch
         return self
 
 
@@ -302,18 +302,20 @@ def __init__(self, *args, **kwargs):
         self.models = []
 
         if len(args) < 1:
-            raise CQLEngineException("No model provided.")
+            raise ValueError("No model provided.")
 
         keyspace = kwargs.pop('keyspace', None)
         connection = kwargs.pop('connection', None)
 
         if kwargs:
-            raise CQLEngineException("Unknown keyword argument(s): {0}".format(
+            raise ValueError("Unknown keyword argument(s): {0}".format(
                 ','.join(kwargs.keys())))
 
         for model in args:
-            if not issubclass(model, models.Model):
-                raise CQLEngineException("Models must be derived from base Model.")
+            try:
+                issubclass(model, models.Model)
+            except TypeError:
+                raise ValueError("Models must be derived from base Model.")
 
             m = models._clone_model_class(model, {})
 
@@ -390,7 +392,8 @@ def _execute(self, statement):
         if self._batch:
             return self._batch.add_query(statement)
         else:
-            result = _execute_statement(self.model, statement, self._consistency, self._timeout, connection=self._connection)
+            connection = self._connection if self._connection else self.model._get_connection()
+            result = _execute_statement(self.model, statement, self._consistency, self._timeout, connection=connection)
             if self._if_not_exists or self._if_exists or self._conditional:
                 check_applied(result)
             return result