The _view_get function is a recursive function used to retieve all the
views related to a view (inherited or t-called).

The issue is that by an odd set of circumstances it is possible to have
a loop in the view graph. Resulting in the recursive function being
called until a "maximum recursion depth exceeded" error occurs.

Example of a loop: A t-call B and A inherit from B

This is possible on an update of a view that has been forked by website:
If the view A was doing a t-call on B and is has been duplicated with
the arch modified.
When we update with the changes A now inherit from B instead of t-call B
Since the arch was modified it will not be updated so A will still
t-call B but the inherit_id of A is unchanged so it will be updated to
reference B resulting in a loop.

closes odoo/odoo#51620

X-original-commit: 63e1e84ebd7e609d6e06d83dc0f0092688b013eb
Signed-off-by: Jérémy Kersten (jke) <jke@openerp.com>

The refactoring also had to be done in order to create a set of unit
tests.
Each behavior can be tested, including the behaviors performed as a
consequence of keyboard interactions (for instance: Enter, Tab...).
This commit also contains some changes to test_utils that were
necessary given the new structure of the wysiwyg editor.

Co-authored-by: Gorash <chm@odoo.com>

* LDAP import: python-ldap is not python3-compatible, pyldap is

  Warning: only supported from debian Stretch (current testing)?
  https://packages.debian.org/search?searchon=names&keywords=pyldap

* implicitly relative imports
* imports of moved or removed stdlib modules

issue #8530