pkgin._check_pkgin(): trivial simplification
requisites.rst: minor copyediting
Finish #5585
Merge pull request #5588 from cvrebert/patch-1

pkgin._check_pkgin(): trivial simplification
Merge pull request #5589 from cvrebert/patch-2

requisites.rst: minor copyediting
Merge branch 'develop' into with-pylint-pragmas