[tox] Update doc testenv to account for documentation restructuring * Build doc from `doc` directory. * Use `sphinx-build` directly instead of `make` as this now works and allows to build within .tox temporary environment (instead of doc/_build), preferable for a "test" action. Related to #5447161.

[schema] drop old backward compat code preventing yams to be itself fully cleaned

[datafeed] allow to use cwclientlib for datafeed's queries (closes #5456849) HTTP based URLs will be handled by a CWProxy if: - cwclientlib is available and - the URL matches a cwclientlibrc config entry Otherwise, fallback to previous implementation. See https://www.cubicweb.org/project/cwclientlib :Warning: This comes with an API modification of DataFeedParser.retrieve_url: it used to accept data and headers arguments to build GET or POST (if data was given) queries, but this was not used by any known code and imply more complicated code.

[cwxml parser] refactor url handling code to use urlparse and urlencode (related to #5456849)

add use_extid_as_cwuri ext entity transform, that will be often necessary and not so easy to write at once

[dataimport] dispatch and deprecate old code previously, the whole dataimport.py content has been copied in dataimport/__init__.py, then dataimport/importer.py API has been introduced. Following these changes, this cset: * dispatch __init__ code into sub-modules * dispatch unittest_dataimport accordingly * deprecates functions and classes that are deprecated by the new API Related to #5414753.

Add tox.ini file * Factor out `commands` for most environments using {envname} substitution to build pytest commande. * Positional arguments are passed on to `pytest` (others may also be passed after a `--`). * Set PATH env variable for tests requiring PostgreSQL. * Also added a `doc` target to build the book. Also update .hgignore exclude .tox directory (where virtualenvs will be created and cubicweb.egg-info created by sdist command). Closes #5447161.

Add requirements.txt files in test directories These files, located in each test directory (when needed), list test dependencies supplementary to install requirements. Some requirements.txt files include psycopg2 because it won't get installed by logilab-database apparently. Related to #5447161.

Spelling fixes in comments and docstrings

[web/views] Clean up confusing backwards compatibility code Dead code since fbb370195199, related to #4943392.

[server/test] avoid lgdb warnings from str to unicode conversion

[web/test] Modernize unittest_propertysheet.py - remove call to os.makedirs in global scope - fold CACHEDIR as an instance attribute - bonus: use unittest directly instead of lgc.testlib

[web/webconfig] Drop pre-3.9 backward compatibility method "has_resource"

[web] Stop using negative indices with os.stat results The python doc says: More items may be added at the end by some implementations. .st_mtime is also more readable than [-2].

[doc] small rst fixes and cleanups in changelog files Related to #4832808

[doc] make the changelog chapter a one html page Related to #4832808