Trying to fix an error in the pypi-importer

[swedebugia@riseup.net]

Hi :)

I am trying to fix this error in the pypi-importer:

~/src/guix$ ./pre-inst-env guix lint python-twisted
gnu/packages/python.scm:6628:0: python-twisted-15.5.0: all the source 
URIs are unreachable:
gnu/packages/python.scm:6628:0: python-twisted-15.5.0: URI 
https://pypi.python.org/packages/source/T/Twisted/Twisted-15.5.0.tar.gz 
not reachable: 404 ("Not Found")
-> it should be .tar.bz2* but the pypi-importer hardcodes tar.gz in 
guix/build-system/python.scm:

(define (pypi-uri name version)
   "Return a URI string for the Python package hosted on the Python 
Package
Index (PyPI) corresponding to NAME and VERSION."
   (string-append "https://pypi.python.org/packages/source/"
                  (string-take name 1) "/" name "/"
                  name "-" version ".tar.gz"))

I read up on if-else with Guile and changed it to:
(define (pypi-uri name version ending)
   "Return a URI string for the Python package hosted on the Python 
Package
Index (PyPI) corresponding to NAME and VERSION."
   (if (zero? ending)
       (string-append "https://pypi.python.org/packages/source/"
                  (string-take name 1) "/" name "/"
                  name "-" version ".tar.gz"))
   (else
       (string-append "https://pypi.python.org/packages/source/"
                  (string-take name 1) "/" name "/"
                  name "-" version "." ending )))

Will this work?
I did a make and got:
   GUILEC guix/build-system/python.go
guix/build-system/python.scm:51:2: warning: possibly unbound variable 
`else'
wrote `guix/build-system/python.go'

The goal was to change in a way that would not break all other calls to 
the procedure pypi-uri.

Any thoughts?

* see https://pypi.python.org/pypi/Twisted/json