Describes the cause and action for error messages.
Error Message(English)：
pull request cannot add reviewers
About pull request reviews - GitHub Help
https://help.github.com/en/articles/about-pull-request-reviews
Enabling required reviews for pull requests - GitHub Help
https://help.github.com/en/articles/enabling-required-reviews-for-pull-requests
Adding a Reviewer to a GitHub Pull Request - Stack Overflow
https://stackoverflow.com/questions/32262295/adding-a-reviewer-to-a-github-pull-request
How to resume review process after updating pull request at ...
https://stackoverflow.com/questions/40893008/how-to-resume-review-process-after-updating-pull-reques・・・
Is it possible to add "Reviewers" through a Github pull request ...
https://stackoverflow.com/questions/43475890/is-it-possible-to-add-reviewers-through-a-github-pull-r・・・
GitHub pull request reviews line comments behaviour
https://stackoverflow.com/questions/39514163/github-pull-request-reviews-line-comments-behaviour
How to disable pull requests in GitHub?
https://stackoverflow.com/questions/27957454/how-to-disable-pull-requests-in-github
Solved: [BitBucket] How could I add a reviewer to a pull r...
https://community.atlassian.com/t5/Bitbucket-questions/BitBucket-How-could-I-add-a-reviewer-to-a-pul・・・
I can't add reviewers in pull request. - Atlassian Community
https://community.atlassian.com/t5/Bitbucket-questions/I-can-t-add-reviewers-in-pull-request/qaq-p/1・・・