Your requirements could not be resolved to an installable set of packages.
Problem 1
- Root composer.json requires phpspec/prophecy ^1.17.0, found phpspec/prophecy[v1.17.0] but the package is fixed to v1.10.3 (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.