This commit introduces a new way to hide a column in a x2m list view.
The attribute 'tree_invisible' can be add in the field attrs in the x2m
view definition. This attribute can use the 'parent' key to make a reference
to the parent record (e.g. 'parent.id').
cgi.escape is unsafe (quote=False by default) and deprecated in Python
3. We already have an openerp.tools.misc.html_escape version which
forwards to the (modern and safe) werkzeug.utils.escape, just use that
everywhere, and convert extant uses of werkzeug.utils.escape to
utils.html_escape as well so that we do the same thing everywhere.
In Python 3, all of these were "consolidated" under urllib(.request,
.parse, .errors) which is inconvenient.
Since we already have hard dependencies on requests and
werkzeug(.urls, which is a backport of Python 3's unicode-aware
urllib.parse) migrate *everything* to that.
A sticking point is urllib2.URLError, those were (mostly) replaced by
the slightly more general IOError which URLError extends.
fwi-odoo