tests: Fix WaitForOneFromTask constructor parameter introspection

Strings are iterable, so the check in WaitForOneFromTask was
effectively useless. This lead to TypeErrors (caught by transition
notifier) when it tried to find None in 'task1'.

Change-Id: I3e91029f7b7cb960d6ca84490de76b5e044bc238

taskflow/tests/utils.py

@@ -15,11 +15,10 @@
 #    under the License.
 
 import contextlib
-
-import collections
-import six
 import threading
 
+import six
+
 from taskflow import exceptions
 from taskflow.persistence.backends import impl_memory
 from taskflow import retry
@@ -317,11 +316,11 @@ class WaitForOneFromTask(SaveOrderTask):
 
     def __init__(self, name, wait_for, wait_states, **kwargs):
         super(WaitForOneFromTask, self).__init__(name, **kwargs)
-        if not isinstance(wait_for, collections.Iterable):
+        if isinstance(wait_for, six.string_types):
             self.wait_for = [wait_for]
         else:
             self.wait_for = wait_for
-        if not isinstance(wait_states, collections.Iterable):
+        if isinstance(wait_states, six.string_types):
             self.wait_states = [wait_states]
         else:
             self.wait_states = wait_states

taskflow/utils/misc.py

@@ -396,7 +396,8 @@ class TransitionNotifier(object):
                 callback(state, *args, **kwargs)
             except Exception:
                 LOG.warn("Failure calling callback %s to notify about state"
-                         " transition %s", callback, state, exc_info=True)
+                         " transition %s, details: %s",
+                         callback, state, details, exc_info=True)
 
     def register(self, state, callback, args=None, kwargs=None):
         assert six.callable(callback), "Callback must be callable"