GitLab

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

- Add types within stcheck.py module
- Update the accept & leave methods signatures inside the VisitableMixIn class
- Redefine type (and set a type alias) for Select.vargraph attribute

Add more types within the following modules:
- rql/utils.py
- rql/interfaces.py
- rql/rqlgen.py

Fixing E402 implied running autopep8 for :
     - E404 from __future__ imports must occur at the beginning of the file
     - E303 too many blank lines

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.

--HG--
branch : stable

--HG--
branch : stable

The old code did:
* forge a string
* eval it as a lamba
* monkey patch classes with the result

We may just drop the logic looping on multiple class by computing class name
dynamically. But this have a different behavior for subclass.

--HG--
branch : stable

--HG--
branch : stable

--HG--
branch : stable