This library no longer supports Python 2, thus usage of six can be
removed. This also removes workaround about pickle library used in
Python 2 only.

Change-Id: I19d298cf0f402d65f0b142dea0bf35cf992332a9

ABCs in collections should be imported from collections.abc and direct
import from collections is deprecated since Python 3.3.

Closes-Bug: #1936667
Change-Id: Ia6316894a67cc0ea7ee0d2110565b45546c813e7

The networkx 2.x series has been out for two years now and supports
python 3.6 and greater[1]. This patch updates TaskFlow to require
a minimum of networkx 2.1. It also updates the code to support
recent deprecation expiration introduced in the 2.4 release.

[1] https://networkx.github.io/documentation/stable/news.html

Change-Id: Ife31d353ba80824ebc63c8b21ee90943badc8da3

With the release of NetworkX 2.0 the reporting API was
moved to view/iterator model. Many methods were moved from
reporting lists or dicts to iterating over the information.
Methods that used to return containers now return views and
methods that returned iterators have been removed in networkx.
Because of this change in NetworkX 2.0 , taskflow code
have to be changed also to support networkx > 2.0

Change-Id: I23c226f37bd85c1e38039fbcb302a2d0de49f333
Closes-Bug: #1778115

Oslo.utils provides same function and just use it.

Change-Id: Iac245d4d98c41edea5294a4d8842db69a42b3794

For a local process based executor usage currently to ensure
that task emitted notifications are proxied we use the multi
processing library and use its queue concept. This sadly creates
a proxy process that gets associated, and this proxy process
handles the queue and messages sent to and from it. Instead of
doing this we can instead just create a temporary local socket
using a random socket and have tasks (which are running in
different processes) use that to communicate back any emitted
notifications instead (and we can use the asyncore module to handle
the emitted notifications since it handles the lower level socket
reading, polling and dispatching).

To ensure that the socket created is somewhat secure we use a
similar process as the multi-processing library uses where we
sign all messages with a hmac that uses a one time key that only
the main process and the child process know about (and reject
any messages that do not validate using this key).

Change-Id: Iff9180054bf14495e5667af00ae2fafbdbc23791

Change-Id: Id9adbc50bd51adc77ce88f698ad0ea2ee63fc5e2

Under some cirumstances it is ok to recompute
a value when raced to by multiple threads, for these
cases allow the cachedproperty to avoid needing and
using a lock.

Change-Id: Icb71cb5ea280185cfb120671be900435dabcd50b

Christmas came early.

Closes-Bug: #1479466

Change-Id: I931d826690c925f022dbfffe9afb7bf41345b1d0