Fixes <http://bugs.gnu.org/21675>.
Reported by Cyril Roelandt <tipecaml@gmail.com>.
Before this change, the command:
guix build python2-oslo.utils -n --no-substitutes
would take 17.5s. After, it is down to 2.9s.
Likewise, the command:
guix graph python2-bandit | grep python2-setuptools.*Helve| wc -l
would return 412 nodes before, all functionally equivalent, and returns
a single one now.
* guix/build-system/python.scm (package-with-explicit-python): Remove
'p' parameter. Change to return a one-argument memoizing procedure.
(package-with-python2): Adjust accordingly.
b3e2a5af9f