@Haypo I have implemented ROUND_UP in pytime.h and pytime.c following your instructions and substitute the usage of ROUND_CEILING in the select module. Please, if you are happy with this implementation, check that the usage of the new ROUND_UP is correct (I think it is but maybe I am missing something).

@serhiy-storchaka I have updated the test so it takes into account more infinite timeout values.

If you prefer a different implementation or use this in more/less places, say so and I will update this PR.

Thank you for your time reviewing this PR! 😄