rpm --httpproxy $http_proxy --import http://download.fedora.redhat.com/pub/fedora/linux/extras/RPM-GPG-KEY-Fedora-Extras error: http://download.fedora.redhat.com/pub/fedora/linux/extras/RPM-GPG-KEY-Fedora-Extras: import read failed(-1). rpmk: url.c:103: XurlFree: Assertion `u && u->magic == 0xd00b1ed0' failed. Aborted Reproducibility: 100%
The option --httpproxy is almost certainly not what you want, what's implemented is a TIS proxy from ~1998.
Since the issue of rpm being network aware is controversial and unlikely to change even gradually this decade, I suggest that you use alternative means of transport that handle modern proxies, and then import as a secondary step. DEFERRED until the rpm development/upgrade glaciers melt in the year 2020 ...