Package error in 8.x

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

  Problem 1
    - Installation request for drupal/codemirror_field ^1.0@RC -> satisfiable by drupal/codemirror_field[1.0.0-rc1].
    - drupal/codemirror_field 1.0.0-rc1 requires codemirror/codemirror ^4.12 -> no matching package found.

Potential causes:
 - A typo in the package name
 - The package is not available in a stable-enough version according to your minimum-stability setting
   see <https://getcomposer.org/doc/04-schema.md#minimum-stability> for more details.

Read <https://getcomposer.org/doc/articles/troubleshooting.md> for further common problems.

Installation failed, reverting ./composer.json to its original content.

I will download manually and see if there's anything obvious causing this issue.