Extend and improve failure logging

Add the ability to show the intention, result,
and state of predecessors of the atom that has failed
so that more contextual information can be shown in the
logs that are written.

Change-Id: Ic77c0d4e94a147e54da74976c1d148aef82eccb3

taskflow/utils/misc.py

@@ -60,6 +60,14 @@ class StrEnum(str, enum.Enum):
         return super(StrEnum, cls).__new__(cls, *args, **kwargs)
 
 
+class StringIO(six.StringIO):
+    """String buffer with some small additions."""
+
+    def write_nl(self, value, linesep=os.linesep):
+        self.write(value)
+        self.write(linesep)
+
+
 def match_type(obj, matchers):
     """Matches a given object using the given matchers list/iterable.