Why am I seeing an “It is suggested to upgrade your index to support normalized names as the name in /simple/{name}.” error message when trying to install pypi packages?

When attempting to set up and work with a remote pypi repository, you might see something like the following error:

DEPRECATION: Failed to find ‘<package-name>’ at <pypi resolution-path>. It is suggested to upgrade your index to support normalized names as the name in /simple/{name}.


This error is caused by a bad URL in your remote repository.  Make sure that the URL of the remote repository is pointing to “https://pypi.python.org”, and that you have not added anything else to the end of it.  e.g.: using “https://pypi.python.org/pypi” will cause this error.