Describes the cause and action for error messages.
Error Message(English)：
cannot reopen pull request
Unable to re-open an accidentally-closed issue or pull request - GitHub
https://github.com/gitbucket/gitbucket/issues/378
GitHub: Reopening a merged pull request - Stack Overflow
https://stackoverflow.com/questions/12674304/github-reopening-a-merged-pull-request
Reopen a pull request on Github
https://stackoverflow.com/questions/53735216/reopen-a-pull-request-on-github
How to remove/replace commit from closed pull request on ...
https://stackoverflow.com/questions/48966565/how-to-remove-replace-commit-from-closed-pull-request-o・・・
Reopen a Pull Request
https://stackoverflow.com/questions/44301363/reopen-a-pull-request
Closing, then reopening a pull request with some new commits ...
https://stackoverflow.com/questions/29905963/closing-then-reopening-a-pull-request-with-some-new-com・・・
Github unable to reopen a closed pull request ? Jason Noble's ...
http://jasonnoble.org/2012/09/github-unable-to-reopen-a-closed-pull-request.html
プルリクエストの画面でMerge出来ない事がわかった場合にどうすればよい ...
https://qiita.com/mapyo/items/a3ab9ef0c011b6757d49
Closing and Reopening a Pull Request - Squirrel University
https://zippyzsquirrel.github.io/squirrel-u/1_SquirrelU/4_GitHub/2_basicConcepts/6_ApproveMerge/