Create a way for a publisher to find the exact cause why they are not allowed to publish a package under a certain name #18362
Description
What's the problem this feature will solve?
TL;DR: Add ability to get a clear indicator why you are not allowed to publish a package
When I was publishing a package for the first time I was getting permission denied error saying that my account is not allowed to publish the package under this name. The error message was leading me to https://pypi.org/help/#project-name. However, it lists many possible reasons why you might not be allowed to publish the package with this name. I tried checking https://pypi.org/project/<my_package_name>/ and searching on https://pypi.org/ by the name of the package and there were no results. In the end I figured out that another person in my organization has claimed this name. It would be nice, if there were a way to figure out what is the exact reason why you cannot publish such a package.
Describe the solution you'd like
Ideally, the error message should contain the exact reason and if the package is already claimed by somebody it should reference a page where you can see the details, ideally the owner you could contact.
If there was a way just to check whether the package name is claimed or not, that would be a nice minimum bar.