The repr format of datetime.timedeltas has changed in Python 3.7, and the
construct is very unsafe anyway.

silent deprecation warnings.

makes swh-vault's tests a bit easier to write.

related to T1265.

used to initialise a database for a given (swh) module, like:

  swh-db-init storage

based on sql files shipped within the python package. This require several
small refactorings of SingleDbTestFixture.setUpClass and .add_db() methods:

- replace the 2 arguments (dump, dump_type) by a single 'dumps' one; this later
  must be an iterable of couples (dump_file, dump_type)
- refactor all needed helper functions accordingly.

We also add a small helper function to sort numerical file names, and provide a
DB_DUMP_TYPES as a global variable to prepare the next commit in which a new
cli tool 'swh-db-init' is added.

Related to T1265.

it's at best useless.

Related D507

Summary:
This helps potentially change the test runner to something other than
nose (T1261).

Test Plan: make test before and after the change both run 26 tests

Reviewers: #reviewers!

Differential Revision: https://forge.softwareheritage.org/D516

Summary: This moves the interesting parts of D505 into the core, so other components can use them as well.

Test Plan: `make test`

Reviewers: ardumont, seirl, #reviewers

Reviewed By: ardumont, #reviewers

Subscribers: douardda

Differential Revision: https://forge.softwareheritage.org/D507

- add classifiers informations,
- add the content of the README file as long_description,
- add configure_urls.

related to T1242

note that unit tests are executed via pifpaf, so a running postgres
server is not required (nor used) when unit tests are spawn with tox.

Also add .tox in gitignore.

Related T1061

Summary:
when ON_ERROR_STOP is not set, dumps can restore even if there's a
syntax error. That's not really a sensible thing to do.

Also add --no-psqlrc because my psqlrc has stuff in it that makes psql noisy in
batch mode (\timing).

Test Plan:
Run the swh-vault tests, which are the only ones to use this fixture
in this mode

Reviewers: #reviewers!

Differential Revision: https://forge.softwareheritage.org/D307

Related T1036

Related T1036

change cherry picked from python module template
commit 71b117ba0cf9f1251b1cac26d0994df03a4c787d