Linting stage in the CI failed

[v1v]

Linting failed with:

[2021-12-16T17:45:07.296Z] 14 files would be left unchanged.
[2021-12-16T17:45:07.296Z] nox > flake8 --ignore=E501,W503 noxfile.py tests/ ecs_logging/
[2021-12-16T17:45:08.243Z] nox > mypy --strict --show-error-codes --no-warn-unused-ignores ecs_logging/
[2021-12-16T17:45:10.160Z] ecs_logging/_stdlib.py:115: error: Argument "style" to "__init__" of "Formatter" has incompatible type "str"; expected "Union[Literal['%'], Literal['{'], Literal['$']]"  [arg-type]
[2021-12-16T17:45:10.160Z] Found 1 error in 1 file (checked 5 source files)
[2021-12-16T17:45:10.160Z] nox > Command mypy --strict --show-error-codes --no-warn-unused-ignores ecs_logging/ failed with exit code 1
[2021-12-16T17:45:10.160Z] nox > Session lint failed.
script returned exit code 1

[v1v]

See #75

[basepi]

This is due to an upstream change. I'm exploring solutions here: #77