gnocchi 4.4.0

- drop python2 support
- remove cradox support

In the StatusController the statistics for the
members on python3 is a byte string which cannot
be jsonified.

This changes so it loops through the statistics
for the member and ensures the key is a string
and not a byte string.

This reverts commit 1daba130be03f8bcc2654677ad9b69db70bb74ce.

Update the docs etc. to use rados directly.

Under newer MySQL versions check constraints are supported and
must have unique names.

Drop and re-create the check constraints on the resource and
resource_history tables to ensure that they are uniquely named
for upgrades in existing deployments.

Ensure that check constraints are created with unique names in
new deployments.

Debug causes Travis to drop the job because
there is to much output.

This reverts commit df3ed0a4a2772ca6224cb4a9c3093a7f1d728c6f.

There is a issue when executing pifpaf directly
from tox, something with psutil/subprocess interaction
that makes it not find the run-upgrade-tests.sh script.

These are treated as error, suppress for now
and we can go back and fix docs later.

This is the current hosting platform now that the name has expired.

- force upgrade of six
- remove README.rst cleanup as it's been done permanently (and i didn't
realise this line existed when i did it)
- add skip_existing[1]. each ENV runs the deploy so travis tries to
upload multiple times and fails on each ENV except for the first

[1] https://docs.travis-ci.com/user/deployment/pypi/#upload-artifacts-only-once

it's not installing correct version when it installs twine during
deploy

- don't concat the values when getting unique times across series
- create a common sum function instead of making a sum timeseries and
ripping out just the values.
- fix test