[repo] Drop _get_session method
it's not actually necessary but holds underlying _sessions dict handling.
Drop backward compat relying on it (which IMO should not be a problem).
Drop import of unused QueryError along the way.
Document: cubicweb-doc
Title: CubicWeb Documentation
Author: Logilab
Abstract: Some base documentation for CubicWeb users and developpers
Section: Apps/Programming
Format: HTML
Index: /usr/share/doc/python-cubicweb-documentation/html/index.html
Files: /usr/share/doc/python-cubicweb-documentation/html/*