[pylint] remove abstract-method warning This kind of message is targeted: "Method 'entity_call' is abstract in class 'EntityView' but is not overridden (abstract-method)" For now, only "entity_call" and "render_body" are dealt with, the list can be extended.

[pylint] upgrade pylintext plugin

update and enhance pylintrc

[schema] use json to serialize constraints Require yams 0.43: constraints are serialized to json, which means we need to recreate the actual checks in the database on upgrade. Temporary deps in tox.ini to pull respective changes in yams.

[pkg] fix cubicweb.spec syntax (grafted from 3309ddb970594cd54529f5c205d1ea5b5da4131e)

[pkg] Use Twisted < 16.0.0 We have some test failures with 16.0.0, such as: - test_put_content (unittest_server.ETwistHTTPTC) - test_base_url (unittest_httptest.TwistedCWAnonTC) (grafted from 10c12f31d0fe38c2e8814176fc42bf2ea210efdf)

[pkg] fix cubicweb.spec syntax

[cwconfig] Use imp.load_source instead of exec() to load site_cubicweb.py from apphome Lets us return a module object and go back to the previous code in CubicWebConfiguration._load_site_cubicweb.

[cwconfig] Stop using lgc.modutils to load *config.py and *ctl.py files

[cwconfig] Stop using lgc.modutils to load site_cubicweb.py files config.load_site_cubicweb function now takes a list of cubes (instead of paths) and default to all known cubes.