task: 51094

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.

In Python 3:

* various builtins and dict methods were changed to return
  view/iterable objects rather than lists
* and the separate Python 2 view/iterable builtins and methods were
  removed altogether

This is problematic when using these items as list (which the happens
repeatedly in Odoo), but more viciously when iterating *multiple times*
over them (which also happens, which I've messed up multiple times while
writing this, and which is a pain to debug even when you've just created
the issue).

Convert all code using these to semantics-matching cross-version
helper functions to get the LCD behaviour between P2 and P3, and
forbid the builtins via lint.

issue #8530

A big section of code was wrongly indented (1 level too much).
The method was returning after 1 iteration of the loop.

Closes #14764