Dear Maintainer,

The manpage says for this option:
     --all, -a
              perform checks with possible side effects, including executing code or modifying files from the current directory.  (equiva‐
              lent: --flags +dangerous --flags +modify)

invoked (in a pbuilder environment:)

#check-all-the-things --all
usage: check-all-the-things [-h] [--jobs [N]] [--checks selectors] [--flags selectors] [--all] [--interrupt {quit,exit,skip}]
                            [--interrupt-period N] [--silent-checks {show,hide}] [--remarks-lines N] [--commands {run,show}]
                            [--checks-output-lines N] [--distro {debian}] [--release {jessie}] [--mime] [--no-mime]
check-all-the-things: error: argument --all/-a: unknown flag: dangerous