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

[langziyang]

trafficstars

Problem 1
    - Root composer.json requires sylius/paypal-plugin 1.5.2 -> satisfiable by sylius/paypal-plugin[v1.5.2].
    - sylius/paypal-plugin v1.5.2 conflicts with behat/mink-selenium2-driver >=1.7.0.
    - behat/mink-selenium2-driver is locked to version v1.7.0 and an update of this package was not requested.

rm -rf ~/.composer && composer req sylius/paypal-plugin:1.5.2 --with-all-dependencies