Partly fixes <http://bugs.gnu.org/20402>.
Reported by Joshua Randall <jcrandall@alum.mit.edu>.
* guix/build/download.scm (open-connection-for-uri): Rewrite to be a
small wrapper around 'open-socket-for-uri'. This procedure was
initially introduced in d14ecda to work around the lack of NSS modules
during bootstrap but that has become unnecessary since 0621349, which
introduced a bootstrap Guile that uses static NSS modules (from commit
d3b5972.)
On Guile >= 2.0.10, this allows the 'http_proxy' environment variable
to be used.
d17551d943