Error consolidation/annotated-command Trying to install Drush using Composer, i get an error concerning consolidation/annotated-command. What does it mean "locked at 2.0.3" and "requires 2.8.1"?

This is the error:

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

  Problem 1

- Installation request for drush/drush dev-master -&gt; satisfiable by drush/drush[dev-master].
- Conclusion: remove consolidation/annotated-command 2.0.3
- Conclusion: don't install consolidation/annotated-command 2.0.3
- drush/drush dev-master requires consolidation/annotated-command ^2.8.1 -&gt; satisfiable by consolidation/annotated-command[2.8.1, 2.8.2].
- Can only install one of: consolidation/annotated-command[2.8.1, 2.0.3].
- Can only install one of: consolidation/annotated-command[2.8.2, 2.0.3].
- Installation request for consolidation/annotated-command (locked at 2.0.3) -&gt; satisfiable by consolidation/annotated-command[2.0.3].

Installation failed, reverting ./composer.json to its original content.
I get this error after changing the minimum version of drush/drush to ~9.0 in my composer.json and running composer update drush/drush afterwards. 

I solved it by just executing composer require drush/drush:~9.0 which lead to the error message drush/drush 9.5.x-dev requires symfony/config ^3.4, so I had to execute composer require symfony/config:^3.4 before composer require drush/drush:~9.0 could be finished successful.

Don't know if this is the only way or best practice to solve such a dependency conflict but in short this worked for me:


composer require symfony/config:^3.4
composer require drush/drush:~9.0