While moving a Pantheon site to Drupal 10 I removed "pantheon-upstreams/upstream-configuration" in order to be able to upgrade.
Trying to add this back after the Drupal 10 upgrade on my local development environment I end up with this:
composer require "pantheon-upstreams/upstream-configuration"
Your requirements could not be resolved to an installable set of packages.
Problem 1
- Root composer.json requires pantheon-upstreams/upstream-configuration * -> satisfiable by pantheon-upstreams/upstream-configuration[dev-master, dev-DPL-1779].
- pantheon-upstreams/upstream-configuration[dev-master, dev-DPL-1779] require drupal/core-composer-scaffold ^9 -> found drupal/core-composer-scaffold[9.0.0-alpha1, ..., 9.5.x-dev] but it conflicts with your root composer.json require (^10.0).
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 pantheon-upstreams/upstream-configuration:*" to figure out if any version is installable, or "composer require pantheon-upstreams/upstream-configuration:^2.1" if you know which you need.
While moving a Pantheon site to Drupal 10 I removed "pantheon-upstreams/upstream-configuration" in order to be able to upgrade.
Trying to add this back after the Drupal 10 upgrade on my local development environment I end up with this: