merge 3.20.14 in 3.21 branch

Added tag 3.20.14, debian/3.20.14-1, centos/3.20.14-1 for changeset f66a4895759e

[pkg] 3.20.14

[tox] use master URL for yams repository No need to clone from review. This should help get consistent results.

[pylint] Avoid invalid-name on schema relation class names

[pylint] more work on the pylint support * uniformize usage of ClassDef and simplify related import * don't insert in the ast a python function but an astroid representation of that function * ignore __pkginfo__ file * drop attr-rgx, variable-rgx and argument-rgx, put the name in good-names instead * drop additional-builtins * add cell_call to the list of methods for which we don't want 'abstract-method'

[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.