The master branch of Monolog has some breaking changes discussed in Seldaek/monolog#903

We should open a PR on branch 3.4 that allows ~2.0 of monolog/monolog and make it green, ie fix our handlers to make them compatible with both versions.

We can also consider Monolog 2 compat as a new feature for 4.2. That'd be less friendly as ppl using 3.4 won't be able to use Monolog 2.

WDYT?