Since https://github.com/zopefoundation/ZODB/commit/a94d63c552d6 (part
of https://github.com/zopefoundation/ZODB/pull/368) some ZODB tests are
marked as being long to help skipping them easily during development via
running tests only at level 1.

But by default we want to continue to run all tests.

-> Adjust tox to run tests at all levels explicitly, since
zope-testrunner's default is to run tests at level 1 only.

--------
kirr:

Those methods are not private to Protocol, because they are invoked e.g. from
other modules besides ZEO.asyncio.base - e.g. from ZEO.asyncio.server . Make
them public via dropping "_" prefix and naming them using more descriptive names.

Extracted from https://github.com/zopefoundation/ZEO/pull/195

--------
kirr:

Always use appropriate logger object set up in a module. It was only
ZEO/tests/ConnectionTests.py which was using logging directly even
though corresponding logger object was set up in that module.

Extracted from https://github.com/zopefoundation/ZEO/pull/195

--------
kirr:

Extract from https://github.com/zopefoundation/ZEO/pull/195 bits that
add documentation to existing code without changing semantic, and fix
typos.

The only things I added myself with further help from @d-maurer are:

- documentation for server_sync in ClientStorage;
- stub documentation for credentials in ClientStorage.

Even though we agree to deprecate credentials in favour of peer-to-peer
TLS, removing their support should go as a separate step.

For server_sync feature, that
https://github.com/zopefoundation/ZEO/pull/195 currently removes, we
actually do use it for correctness:

https://lab.nexedi.com/nexedi/erp5/blob/eaae74a082a0/product/ERP5Type/tests/custom_zodb.py#L175-179
nexedi/erp5@c663257f
https://github.com/zopefoundation/ZODB/commit/9821696f584f

So document it with the intent to preserve it.

/reviewed-on https://github.com/zopefoundation/ZEO/pull/202

We can use stdlib random module and manually adjust randint to behave
exactly as before Python3, so that testdata are matched exactly as before.

Also drop unnecessary `random.seed(42)` in cache_run. It is not needed
there because random is not used in cache_run at all.

Based on work of @d-maurer in https://github.com/zopefoundation/ZEO/pull/195 .

Reduce ZEO testing time by dropping tests with some storages

Drop ZEO tests with storages `DemoStorage`, `FileStorage` and `HexFileStorage`; `FileStorage` is still tested in the variants with server side blobs and with shared blobs

Full linting with flake8

Co-authored-by: Dieter Maurer <d-maurer@users.noreply.github.com>

Co-authored-by: Dieter Maurer <d-maurer@users.noreply.github.com>

Configure with zope.meta.config.config-package

Python 3.10 support

tpc_vote/abort + log message enhancements

Remove testing for mtacceptor and dead Python versions

Python 3.10 distinguishes SSL contexts for server and client use - and SSL fails with the wrong context type

#165 more accurate asyncio.CancelledError handling