ENH: Consider warnings as errors when running pytest

[jhlegarreta]

Consider warnings as errors when running pytest: add the strict-warnings flag to pytest to consider warnings as errors.

[oesteban]

pytest: error: unrecognized arguments: --strict-warnings
  inifile: /src/mriqc/pyproject.toml
  rootdir: /src/mriqc

[jhlegarreta]

Yes, there is efforts across other NiPreps repositories to enforce this as well, e.g.
nipreps/nireports#157
nipreps/nifreeze#40

Only the latter seems to be working. There is a discussion with Chris on the nireports PR. It may be worthwhile going over this during the next tech meeting to avoid accumulating technical debt.

PS: Unrelated to the topic and suitable for a tech meeting: should the default branch be renamed to main for the sake of consistency with modern practices/other NiPreps repositories?

[jhlegarreta]

The CircleCI build error seems to be unrelated:
https://app.circleci.com/pipelines/github/nipreps/mriqc/1726/workflows/0319bd79-0c48-43be-9d23-5bd2a953e62d/jobs/10512?invite=true#step-111-53041_161

The URL seems to exist:
https://app.circleci.com/pipelines/github/nipreps/mriqc/1726/workflows/0319bd79-0c48-43be-9d23-5bd2a953e62d/jobs/10512

I ignore why curl is failing.

Until we solved that, I cannot provide evidence that the patch set in this PR works as expected.