Failed to execute git checkout '787a8092d34f577adb99fb74f6ad45123851efd8' -- && git reset --hard '787a8092d34f577adb99fb74f6ad45123851efd8' -- fatal: reference is not a tree: 787a8092d34f577adb99fb74f6ad45123851efd8 It looks like the commit hash is not available in the repository, maybe the commit was removed from the branch? Run "composer update php-http/promise" to resolve this.