- update tox configuration, add black environment
- format the whole project
- update Gitlab CI config add a job for black

This allow pip to install a older python2 compatible package if running with python2.
The "Programming Language :: Python :: 3 :: Only" is just for pypi statistics AFAIK.

Move sources to a 'rql' subdirectory, drop the NO_SETUPTOOLS code path
(essentially rewriting all of setup.py).  This avoids a conflict between
our parser.py and the stdlib when running setup.py.  Closes #278637.

Requires python >= 2.6.

And use it in the Debian packaging to make sure we don't end up with a
disfunctional package.
Closes #159003

In some cases (eg, windows without Visual Studio installed),
distutils/setuptools build_ext.run() may raise exceptions other than
CompileError. By catching all exceptions, we can make sure rql's
setup.py never fails, which should help dumb package managers such as
pip.