pypi-uri

[Danny Milosavljevic]

Hi,

>> Can you change this to use 'pypi-uri' instead?  
> Any reason why `guix import` doesn't do that by default? I just copied
> the output from that command, so I believed it was the way it should
> be done.  

PyPI switched to content-addressing only (with a hash function different from 
ours) and doesn't support fetching a package by name with the usual simple URL 
anymore.  Therefore, we are using pypi.io as an alternative.

Example: 
<https://pypi.python.org/packages/fa/12/4a837dc26173819a29e713cbfb490a83d5296545abbe53422d7b14604d8f/marshmallow-3.0.0b2.tar.gz>
 vs <https://pypi.io/packages/source/m/marshmallow/marshmallow-3.0.0b2.tar.gz>.

Unrelated to this, back in the day I adapted make-pypi-sexp to handle a special 
case (for example for uwsgi):  pypi urls are case-sensitive and for some reason 
in Guix we mangle the package names to be all-lowercase.  That means that 
(naturally) some of the urls returned by pypi-uri don't work because the case 
is different.

So I've adapted make-pypi-sexp to find out whether the pypi-uri and the actual 
source url it just downloaded from agree - and if not, it prefers the latter.  
The latter just worked when downloading it so it's the safe choice.

That said, I've just tried to fetch 
<https://pypi.io/packages/source/u/uwsgi/uwsgi-2.0.15.tar.gz> (note: case is 
wrong, should be "uWSGI") and it works (!).

So I guess we can remove the special case again.