Enable to check package documentation can be built without producing
sphinx warnings.

The sphinx environment is designed to be used in continuous integration
in order to prevent breaking documentation build when committing changes.

The sphinx-dev environment is designed to be used inside a full swh
development environment.

Related to T3258

Like all our internal APIs, it's RPC and not REST.

Related to T1410

Services configuration are mandatory, so merging with default
config can only lead to discrepancies with service that may have
alternative configuration structure.

CLI logging is configured at SWH CLI root.

It's already pulled from swh.core[db] which is a runtime dependency.

Related to T2746

swh.core (0.9.0) changed the remote exception serialization handling.

So the current build [1] is broken as it needs adaptation to retrieve the
exception information at its first level.

This adapts accordingly the exception handling in those failing tests.

[1] https://jenkins.softwareheritage.org/job/DVAU/job/tests/881/

And remove pytest-aiohttp test dependency to avoid error related to double
loading of the plugin when pytest is invoked.

This also fixes the build [1]

Related to 6682bcc9

[1] https://jenkins.softwareheritage.org/job/DVAU/job/tests/875

The checks ensure the virtual config was ok and then went on returning the
initial configuration (which was possibly incomplete).

This commit fixes it.

That will ease instantiation from dict in other locations

Remove the args because it's deprecated

The current implementation fails [1] on current debian stable build. So
simplifying to this is quite enough and should unstuck said build.

[1] https://jenkins.softwareheritage.org/job/debian/job/packages/job/DVAU/job/gbp-buildpackage/41/console

This just drops the redundant `-swh` prefix.

Related to T2736

Keep the old behavior to avoid breakage on part not yet migrated.
Detach configuration checking from instanciation in cookers similarly
to most swh components.

This allows to drop redundant code in between rpc server and clients using the
base class from swh.core.api.async module.

This reuse the swh.core.db.db_utils.SwhDatabasejanitor which allows to truncate
tables in between test calls. This makes the tests faster.

Related to T1410

It enables to remove some code duplication related to git loader creation
when executing tests.

Fixes build [1]

[1] https://jenkins.softwareheritage.org/job/DVAU/job/tests/807/console

Related to T2610

Related to T2610

flake8 hook has been removed from https://github.com/pre-commit/pre-commit-hooks
so now use the one from https://gitlab.com/pycqa/flake8

by moving import statements in functions. Also simplify the main
help message to to get rid of the necessity to import swh.core.config.

Related to T2575.

instead of swh.objstorage (deprecated).

Although that will be fixed in the next version of swh-storage,
the current one returns a None status for skipped content, which
causes surprising behavior from the cooker (as it reuse the content
of the previous file in place of the current one).

Additionally, even though it shouldn't happen, if a content is
missing completely (ie. neither know nor skipped), it's still
possible to have a None status.

pytest wastes a lot of time in .hypothesis and .git; this commit excludes them.

Some tests are now failing since rDMOD6dd6acecc8297f8c9f77bdae0ccd291ceabdfd8e.

This also adds type and simplify the existing code