Enable error warning mode

[fjetter]

There are hundreds of warnings raised when running our test suite. Typically warnings indicate deprecated and/or unsafe behaviour and there is a long term value to cleaning these up.

Particularly py3.10 introduced many DeprecationWarnings that alert us to improper usage of asyncio.

We should enable a strict warning mode with -WError when running our tests.

A first step should be possible by enabling the error and ignoring all known warnings.

Note: dask/dask is not raising for all errors but rather on errors for specific dependencies, see https://github.com/dask/dask/blob/0b36d7fcaf54ee9a78fff4b07f124cb0c8741cdf/setup.cfg#L49-L54

Out of scope

• Fixing all the warnings

In scope

• A plan / follow up tickets to fix warnings