These all introduce or update existing Python Packaging Specifications,
and should follow the PyPA Specification processes. These are expected
to be Standards Track PEPs and are not informational.
This change also ensures that they get listed under the correct section
on the Packaging topic index.
* Reword PEP 503 to match pip's URL lookup behavior
Clarify that the "filename" displayed in the anchor tag refers to the
final path component of the URL (instead of, say, the filename parameter
in the HTTP Content-Disposition header).
This matches pip's behavior: The URL's final path component is used to
determine the artifact's name (for selection), and its filename after
download.
* Replace "an URL" with "a URL"