A quick note for core contributors regarding Drupal 8 issue tags related to the upcoming release candidate phase:

rc deadline issue tag

Issues that are not critical but can only be committed before the first release candidate is released (e.g., issues that change translatable strings or APIs). If they're not finished by the time the release candidate is ready, they must either be postponed to Drupal 8.1.0 or Drupal 9.

rc target issue tag

Rare! Issues that are not critical but can committed during the release candidate phase (for example, documentation changes, certain coding standards improvements, or other issues at committer discretion). Issues with this tag must have committer approval (so check with a committer before adding it).

More information on Drupal 8 release phase issue tags.