Cannot delete old repositories

I want to delete my one of old repositories ,but It prompt :
No source repositories were detected at https://github.com/xxxxx/demopaper2. Please check the URL and try again.

From the screenshot of the error message it looks like you’re trying to IMPORT a repository from another version control system (SVN, Mercurial, etc.), not trying to delete an existing repository.

@sinkiangscorpio try following this link for instructions
deleting-a-repository


when I click cancel button I can visit my repo。
so I can delete this repo