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

Related to T2265

This is needed for the swh-counters module, one backend uses Redis to
manage the counters by themselves, and another one manages the history
files using prometheus.
Each one can possibly evolve separately or can use a different backend
implementation one day or another.

Related to T3165

I don't understand what this library does or why we needed it.
This commit replaces it with the good old functools.wraps(),
which fixes this crash that started occuring with
decorator 5.0.5:

```
ERROR    testapp:app.py:1892 Exception on /foo [POST]
Traceback (most recent call last):
  File "/home/dev/.local/lib/python3.7/site-packages/flask/app.py", line 2447, in wsgi_app
    response = self.full_dispatch_request()
  File "/home/dev/.local/lib/python3.7/site-packages/flask/app.py", line 1952, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/home/dev/.local/lib/python3.7/site-packages/flask/app.py", line 1821, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/home/dev/.local/lib/python3.7/site-packages/flask/_compat.py", line 39, in reraise
    raise value
  File "/home/dev/.local/lib/python3.7/site-packages/flask/app.py", line 1950, in full_dispatch_request
    rv = self.dispatch_request()
  File "/home/dev/.local/lib/python3.7/site-packages/flask/app.py", line 1936, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/home/dev/.local/lib/python3.7/site-packages/decorator.py", line 231, in fun
    args, kw = fix(args, kw, sig)
  File "/home/dev/.local/lib/python3.7/site-packages/decorator.py", line 203, in fix
    ba = sig.bind(*args, **kwargs)
  File "/usr/lib/python3.7/inspect.py", line 3015, in bind
    return args[0]._bind(args[1:], kwargs)
  File "/usr/lib/python3.7/inspect.py", line 2930, in _bind
    raise TypeError(msg) from None
TypeError: missing a required argument: 'self'
```

https://github.com/micheles/decorator/issues/109

There were some typos in the factory's documentation,
and the instances were not documented at all.

Ensure tests can be executed using hypothesis >= 6 by suppressing
the function_scoped_fixture health check on test that uses a function
scope fixture in combination with @given that does not need to be reset
between individual hypothesis examples.

swh.storage will need it to specify explicitly migration files to run.

This fixes build [1]

[1] https://jenkins.softwareheritage.org/view/swh%20master/job/DCORE/job/tests/1183/console

It exists cases where a custom exception type cannot be rebuilt from its
serialized form.

As a fallback, build a base Exception with the message of the serialized
exception.

decoding custom format is still supported for backward compat.

Note that this revision modifies the exception type raised when attempting to
encode a naive datetime object for both formats (json amd msgpack): it now
raises a TypeError instead of a ValueError.

to make it clear which codecs are specific to the json format.

instead of json.dumps(..., cls=SWHJSONEncoder) and so.

This simplify a bit the code and make sure the json_dumps/loads
functions are actually tested.

it should not be used anymore.

we should be free of them by now. The journal has been recreated from
scratch since then.

This allows users to pass multiple --log-level values to the swh cli, to allow
finer grained configuration of the logging of some modules, without having to
resort to a full-fledged, very verbose log config file.

Close T2819.

We now match the command line output per section, in a fuzzier way than before.

The previous implementation would always append extra_encoders to the main
ENCODERS list. Refactor encoder and decoder extensions both with a common getter
which doesn't mutate the global variable.

This is to support some of the metadata imported from npm package.jsons in
revisions.

Those db utilities were only used within swh.core. By dropping those, we can
then stop installing pifpaf within tox for the db tests.

The tests are now probably faster than before as well.

This renames the test file to test_pytest_plugin which is clearer since it
relates to the actual module being tested.

This also moves the tests into its own dedicated arborescence because that's a
different module now.

This drops the pytest-postgresql from requirements-db.txt. This is not a
required dependency for the swh.core.db module itself.

It's a requirement for the swh.core.db.pytest_plugin. This module should become
its own module as a test requirements for other swh modules (including
swh.core.db but not limited to it).

So this commit adds a dedicated requirements-db-pytestplugin.txt file with such
dependency. This opens the db-pytestplugin key within the setup.py and then
references that test dependency for the swh.core.db modules (as it's needed for
tests of the module).

Related to T2746

Reraising exceptions in RPCClient was not honored anymore due to a mistake
introduced in last commit.

An exception can be constructed with another exception argument so handle
that special case by adding a dedicated encoder and decoder to avoid remote
exception serialization error.

This explicitely checks the different scenario possible with the current
subcommands (create, init-admin, init).

Using a subset of sql schema representation we have in our existing datasets.

Closes T2741

Both requests.Request and _pytest.FixtureRequest objects are passed to
test fixtures as argument 'request'. This hurts readability.
Adding typing annotations makes it clear which one is meant.

In staging, the db is already created by puppet, the current create database
stanza forced within the create-db cannot work.

Ths subsequent steps of postgresql extensions installation is required though.

This will allow it.

Related to T2736

Fixes build [1]

[1] https://jenkins.softwareheritage.org/job/DENV/job/tests/lastBuild/artifact/swh-core.log

This also adds more tests around the instantiation of such servers.

Defining 'pytest_plugins' in a non-top-level conftest is no longer supported
because it affects the entire directory tree in a non-explicit way.

This will allow to align the Vault's client/server code with the other rpc
servers. And start adding one typed interface with more consistent checks in
between implementations.

This moves the SWHDatabaseJanitor from swh.storage to swh.core. This also adds
tests to it.

This will allow to share the behavior on other swh services with postgres
backends (vault, scheduler, etc...).