Re: Python 3 binaries

[Andreas Enge <andreas@enge.fr>]

Very well. If we do not wish to make the symlink python->python3,
then we will need special code in patch-shebangs, so that things like
"#!/usr/bin/python" may get rewritten to
"#!/nix/store/...python-3.3.2/bin/python3" if no binary named "python"
is found.

I think the following patch does this:

--- a/guix/build/utils.scm
+++ b/guix/build/utils.scm
@@ -516,7 +516,10 @@ FILE are kept unchanged."
                                  (rest (match:substring m 3))
                                  (has-env (string-suffix? "/env" interp))
                                  (cmd (if has-env arg1 (basename interp)))
-                                 (bin (search-path path cmd)))
+                                 (bin (or (search-path path cmd)
+                                          (if (string=? cmd "python")
+                                              (search-path path "python3")
+                                              #f))))
                             (if bin
                                 (if (string=? bin interp)
                                     #f            ; nothing to do

But it triggers a full rebuild, so it will take me a while to test it.

If you agree to this patch, we would need to revive core-updates, and should
revert to python 2 in master. Could we then build core-updates also on
hydra.gnu.org? This would make it easier to add python modules for the two
different versions.

Andreas