Packaging Tutorial should mention that packages TestPyPI and PyPI are different sets

[pradyunsg]

From pypa/packaging-problems#170

Packages on TestPyPI and PyPI can differ. This can result in a hard-to-debug issue where one is unable to install my-package as dependency is not available on TestPyPI. It's not clear to a first timer that this might happen and what they should do next, since doing pip install dependency would work out for them but the suggested way to test their TestPyPI package won't.

I think there's 2 possible suggestions here:

• Using --no-deps to install the my-package and then doing pip install my-package to install dependency from PyPI.
• Making the user manually install dependency from PyPI then installing my-package from TestPyPI.

I'd prefer the former since there's no need to manually mention the dependencies (assuming it works; I didn't check).

[dstufft]

This is probably covered long term by pypi/warehouse#2286, pypi/warehouse#918, or pypi/warehouse#726.

[pastelmind]

I think this overlaps with #559, which was closed by #593. Should this be closed?