Description of problem:
Upstream bugreports:
https://github.com/ocaml/opam/issues/4888
https://github.com/ocaml/opam/pull/4790

Version-Release number of selected component (if applicable):
2.1.0

How reproducible:


Steps to Reproduce:
1. Add some custom repositories (e.g. follow Fedora instructions from https://vscodium.com/#install)
$ yum repolist
repo id                                                         repo name
fedora                                                          Fedora 35 - x86_64
fedora-cisco-openh264                                           Fedora 35 openh264 (From Cisco) - x86_64
gitlab.com_paulcarroty_vscodium_repo                            gitlab.com_paulcarroty_vscodium_repo
rpmfusion-free                                                  RPM Fusion for Fedora 35 - Free
rpmfusion-free-updates                                          RPM Fusion for Fedora 35 - Free - Updates
updates                                                         Fedora 35 - x86_64 - Updates

$ opam search foo

Actual results:
Takes minutes to provide result. strace shows it is stuck waiting on a pid, and that pid is running 'yum -q -C list'

Expected results:
'opam search foo' completes quickly


Additional info:
Patch available here: https://github.com/ocaml/opam/commit/78093ea4299fb7a50bb5d9e939f39b24bc5cacbe
New upstream release may be available soon
yum -q -C list
Importing GPG key 0x5A278D9C:
 Userid     : "Pavlo Rudyi <paulcarroty>"
 Fingerprint: 1302 DE60 2318 89FE 1EBA CADC 5467 8CF7 5A27 8D9C
 From       : https://gitlab.com/paulcarroty/vscodium-deb-rpm-repo/raw/master/pub.gpg
Is this ok [y/N]: 

'yum -y makecache' doesn't help, and neither does manually answering yes here (on next invocation it'll just ask again).
Upstream patch replaces 'yum' invocation with 'rpm -qa' invocation.