Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - Root composer.json requires rarst/wps * -> satisfiable by rarst/wps[dev-master, 1.0, 1.1, 1.2, 9999999-dev].
    - rarst/wps[1.0, ..., 1.1] require composer/installers ~1.0 -> found composer/installers[v1.0.0, ..., 1.x-dev] but the package is fixed to v2.3.0 (lock file version) by a partial update and that version does not match. Make sure you list it as an argument for the update command.
    - rarst/wps[dev-master, 1.2] require composer/installers ~1.6 -> found composer/installers[v1.6.0, ..., 1.x-dev] but the package is fixed to v2.3.0 (lock file version) by a partial update and that version does not match. Make sure you list it as an argument for the update command.

Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.
You can also try re-running composer require with an explicit version constraint, e.g. "composer require rarst/wps:*" to figure out if any version is installable, or "composer require rarst/wps:^2.1" if you know which you need.

Installation failed, reverting ./composer.json and ./composer.lock to their original content.