Remove unused utility classes

Removing ThreadGroupExecutor allows to get rid of threading2
dependency. LastFedIter is also not used, so there is no
reason to keep it.

Change-Id: Id396ab59ebf1e2314ef620417d7cac09e1ab8d3b

taskflow/utils/misc.py

@@ -155,21 +155,6 @@ class TransitionNotifier(object):
                 break
 
 
-class LastFedIter(object):
-    """An iterator which yields back the first item and then yields back
-    results from the provided iterator.
-    """
-
-    def __init__(self, first, rest_itr):
-        self.first = first
-        self.rest_itr = rest_itr
-
-    def __iter__(self):
-        yield self.first
-        for i in self.rest_itr:
-            yield i
-
-
 class Failure(object):
     """Indicates failure"""
     # NOTE(imelnikov): flow_utils.FlowFailure uses runner, but

taskflow/utils/threading_utils.py

@@ -18,7 +18,6 @@
 
 import logging
 import threading
-import threading2
 import time
 import types
 
@@ -121,32 +120,6 @@ class CountDownLatch(object):
             return self.count <= 0
 
 
-class ThreadGroupExecutor(object):
-    """A simple thread executor that spins up new threads (or greenthreads) for
-    each task to be completed (no pool limit is enforced).
-
-    TODO(harlowja): Likely if we use the more advanced executors that come with
-    the concurrent.futures library we can just get rid of this.
-    """
-
-    def __init__(self, daemonize=True):
-        self._threads = []
-        self._group = threading2.ThreadGroup()
-        self._daemonize = daemonize
-
-    def submit(self, fn, *args, **kwargs):
-        t = threading2.Thread(target=fn, group=self._group,
-                              args=args, kwargs=kwargs)
-        t.daemon = self._daemonize
-        self._threads.append(t)
-        t.start()
-
-    def await_termination(self, timeout=None):
-        if not self._threads:
-            return
-        return self._group.join(timeout)
-
-
 class ThreadSafeMeta(type):
     """Metaclass that adds locking to all pubic methods of a class"""
 

tools/pip-requires

@@ -7,7 +7,6 @@ sqlalchemy>=0.7,<=0.7.99
 alembic>=0.4.1
 # Very nice graph library
 networkx>=1.8.1
-threading2
 Babel>=0.9.6
 # Used for backend storage engine loading
 stevedore>=0.10