This is a combination of 3 commits that are all needed to unblock gate:

1. Move testing to py36

The base infra images no longer have python 3.5 available and are
all failing. We should be testing on py36 now anyway since that is
the minimum supported version for Train.

2. Stop redis-server before running tests

Just installing redis-server on Ubuntu Bionic starts the service,
which means when we try to start one via pifpaf it fails due to the
port already being in use.

This change adds a pre-run playbook that stops the redis-server
service so ours can run successfully.

3. [stable-only] Cap stestr for python 2

stestr dropped python 2 support with version 3.0.0 and tooz does not
use constraints from openstack/requirements, so test-requirements.txt
is updated to use stestr<3.0.0 in case of python 2.

Since tooz do not consume upper-constraints there is no need for
requirement check job either so it is removed, too.

Conflicts:
    tox.ini
    test-requirements.txt

NOTE(elod.illes):
  * tox.ini conflict is due to py37 is not yet added as tox target in
    Stein.
  * test-requirments.txt is not present in Stein, setup.cfg is used
    instead.

First two commit was squashed in train (original patch's change id is
I3f7f7ea9069d8c890a82f31ad14c9663e98c09dc and cherry picked from commit
8207427fffc72547387369ce7ba2696a86bf7626).

Closes-Bug: 1828610
Change-Id: I7a75be587efc2098e919f1ea34f9ffc357203dfb
(cherry picked from commit 13a6dffa32789ac91b724977ed1d73375baf0824)

Change-Id: I699c698754f498cacff4998f33ea0738682b86e7

This commit was bulk generated and pushed by the OpenDev sysadmins
as a part of the Git hosting and code review systems migration
detailed in these mailing list posts:

http://lists.openstack.org/pipermail/openstack-discuss/2019-March/003603.html
http://lists.openstack.org/pipermail/openstack-discuss/2019-April/004920.html

Attempts have been made to correct repository namespaces and
hostnames based on simple pattern matching, but it's possible some
were updated incorrectly or missed entirely. Please reach out to us
via the contact information listed at https://opendev.org/ with any
questions you may have.

On python2 in case of unicode objects, str() was causing UnicodeEncodeError.
Also utf8 encoding as a default (mostly for Python2)

Change-Id: I64373133f65c5b11daa3462b7c21a55d06738c09

If you're not intimately familiar with RFC 1808 it can be a bit tricky to
write tooz connection strings. In addition, some drivers do not document the
options that they recognize in a connection string. This can force a user to
read the driver code in order to figure out how to configure tooz to use said
driver, which should not be the case.

This change more explicitly documents the format of the connection string,
including which parts of an RFC 1808 URI it recognizes, and the options that
can be passed. It also clarifies which parts of the connection string are
optional (possibly because they have defaults) and which must always be
included.

Note that not every possible configuration is documented. For example, the
postgres driver supports multiple methods of configuring the connection host
and port. For consistency, I only documented the one that matches the other
drivers. This should be sufficient to allow a user to write a working
connection string.

This change also wires the etcd3 and etcd3gw drivers into the doc index since
they were missing before.

Change-Id: I66e54433115f27fb54badc2173f8f6044c49aacb

We have a couple of issues blocking tooz test jobs right now. This
is a combination of two commits that fix the problem.

Cap grpcio<1.16.0

1.16.0 introduces a bug that is causing our etcd3 tests to fail on
a consistent basis. Until that is resolved we can't use any higher
versions of grpcio.

1.0.0 is used as the lower bound on the assumption that any version
of the current major release will work. Since we weren't setting a
bound before that seems relatively safe.

Partial-Bug: 1808046

Fix requirements

The requirements check job is failing on a couple of the entries in
this project. enum34 needs a lower bound, and futurist has an
exclusion that isn't in global-requirements.

enum34 is given the same lower bound as oslo.upgradecheck, and
futurist's lower bound is increased to the last global lower bound
(before lower bounds were removed), which eliminates the need for
the exclusion.

Change-Id: I1b279e138325b596f5ec2c61717029d2f7bdd075
Depends-On: https://review.openstack.org/#/c/624759/

Mailinglists have been updated. Openstack-discuss replaces openstack-dev.

Change-Id: I136c931dce4927c500e29205b8cddf04533f8d83