Pass WriteType, not str to RetryPolicy.on_write_timeout

Fixes #123

CHANGELOG.rst

@@ -10,6 +10,9 @@ Bug Fixes
 ---------
 * Don't strip trailing underscores from column names when using the
   named_tuple_factory (PYTHON-56)
+* Pass WriteType instance to RetryPolicy.on_write_timeout() instead
+  of the string name of the write type. This caused write timeout
+  errors to always be rethrown instead of retrying. (github #123)
 
 1.1.2
 =====

cassandra/decoder.py

@@ -43,6 +43,7 @@ from cassandra.cqltypes import (AsciiType, BytesType, BooleanType,
                                 InetAddressType, IntegerType, ListType,
                                 LongType, MapType, SetType, TimeUUIDType,
                                 UTF8Type, UUIDType, lookup_casstype)
+from cassandra.policies import WriteType
 
 log = logging.getLogger(__name__)
 
@@ -291,7 +292,7 @@ class WriteTimeoutErrorMessage(RequestExecutionException):
             'consistency': read_consistency_level(f),
             'received_responses': read_int(f),
             'required_responses': read_int(f),
-            'write_type': read_string(f),
+            'write_type': WriteType.name_to_value[read_string(f)],
         }
 
     def to_exception(self):

cassandra/policies.py

@@ -568,6 +568,14 @@ class WriteType(object):
     internally before a BATCH write.
     """
 
+WriteType.name_to_value = {
+    'SIMPLE': WriteType.SIMPLE,
+    'BATCH': WriteType.BATCH,
+    'UNLOGGED_BATCH': WriteType.UNLOGGED_BATCH,
+    'COUNTER': WriteType.COUNTER,
+    'BATCH_LOG': WriteType.BATCH_LOG,
+}
+
 
 class RetryPolicy(object):
     """