Added a thrown exception when a transaction fails to be applied

.gitignore

@@ -45,3 +45,6 @@ docs/_build
 
 #iPython
 *.ipynb
+
+cqlengine/tests/*
+cqlengine/tests*

cqlengine/exceptions.py

@@ -2,5 +2,6 @@
 class CQLEngineException(Exception): pass
 class ModelException(CQLEngineException): pass
 class ValidationError(CQLEngineException): pass
+class TransactionException(CQLEngineException): pass
 
 class UndefinedKeyspaceException(CQLEngineException): pass

cqlengine/query.py

@@ -6,7 +6,7 @@ from cqlengine.columns import Counter, List, Set
 
 from cqlengine.connection import execute
 
-from cqlengine.exceptions import CQLEngineException, ValidationError
+from cqlengine.exceptions import CQLEngineException, ValidationError, TransactionException
 from cqlengine.functions import Token, BaseQueryFunction, QueryValue, UnicodeMixin
 
 #CQL 3 reference:
@@ -836,6 +836,12 @@ class DMLQuery(object):
             return self._batch.add_query(q)
         else:
             tmp = execute(q, consistency_level=self._consistency)
+            if tmp and tmp[0].get('[applied]', True) is False:
+                tmp[0].pop('[applied]')
+                expected = ', '.join('{0}={1}'.format(t.field, t.value) for t in q.transactions)
+                actual = ', '.join('{0}={1}'.format(f, v) for f, v in tmp[0].items())
+                message = 'Transaction statement failed: Expected: {0}  Actual: {1}'.format(expected, actual)
+                raise TransactionException(message)
             return tmp
 
     def batch(self, batch_obj):