Use six string types instead of basestring

To increase our python3 compatability we should
attempt to use the six module for known issues
that are likely to happen in python3 when comparing
to string types.

Change-Id: Ib6fc32138e218c8b45023ca37d87b742694b8349

taskflow/task.py

@@ -18,6 +18,7 @@
 #    under the License.
 
 import abc
+import six
 
 from taskflow.utils import misc
 from taskflow.utils import reflection
@@ -33,7 +34,7 @@ def _save_as_to_mapping(save_as):
     # returns is pretty crucial for other later operations.
     if save_as is None:
         return {}
-    if isinstance(save_as, basestring):
+    if isinstance(save_as, six.string_types):
         # NOTE(harlowja): this means that your task will only return one item
         # instead of a dictionary-like object or a indexable object (like a
         # list or tuple).

taskflow/utils/misc.py

@@ -22,9 +22,9 @@ from distutils import version
 import collections
 import copy
 import logging
+import six
 import sys
 
-
 LOG = logging.getLogger(__name__)
 
 
@@ -33,7 +33,8 @@ def get_task_version(task):
     task_version = getattr(task, 'version')
     if isinstance(task_version, (list, tuple)):
         task_version = '.'.join(str(item) for item in task_version)
-    if task_version is not None and not isinstance(task_version, basestring):
+    if task_version is not None and not isinstance(task_version,
+                                                   six.string_types):
         task_version = str(task_version)
     return task_version
 
@@ -56,7 +57,7 @@ class ExponentialBackoff(object):
 def as_bool(val):
     if isinstance(val, bool):
         return val
-    if isinstance(val, basestring):
+    if isinstance(val, six.string_types):
         if val.lower() in ('f', 'false', '0', 'n', 'no'):
             return False
         if val.lower() in ('t', 'true', '1', 'y', 'yes'):