Bug 2035507

Description of problem:

I'm unable to build packages in mock for fedora-* (34, 35, or rawhide), whereas epel-7 and 8 are OK.  This is in up-to-date RHEL8.

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

mock-2.15-1.el8

Steps to Reproduce:
1. mock -r fedora-35-x86_64 ...src.rpm

Actual results:

NFO: enabled HW Info plugin
Mock Version: 2.15
INFO: Mock Version: 2.15
Start: dnf install
No matches found for the following disable plugin patterns: local, spacewalk, versionlock
fedora                                               0.0  B/s |   0  B     00:00    
Errors during downloading metadata for repository 'fedora':
  - Curl error (6): Couldn't resolve host name for https://mirrors.fedoraproject.org/metalink?repo=fedora-35&arch=x86_64 [getaddrinfo() thread failed to start]
Error: Failed to download metadata for repo 'fedora': Cannot prepare internal mirrorlist: Curl error (6): Couldn't resolve host name for https://mirrors.fedoraproject.org/metalink?repo=fedora-35&arch=x86_64 [getaddrinfo() thread failed to start]
ERROR: Exception(/home/vagrant/rpmbuild/SRPMS/n-diff-2.00-2.el8.src.rpm) Config(fedora-35-x86_64) 0 minutes 2 seconds
INFO: Results and/or logs in: /var/lib/mock/fedora-35-x86_64/result
ERROR: Command failed: 
 # /usr/bin/systemd-nspawn -q -M 7f3ec1dccd0b412cb567f1d0d3356b86 -D /var/lib/mock/fedora-35-x86_64-bootstrap/root -a --capability=cap_ipc_lock --bind=/tmp/mock-resolv.zlmp6_pc:/etc/resolv.conf --setenv=TERM=vt100 --setenv=SHELL=/bin/bash --setenv=HOME=/var/lib/mock/fedora-35-x86_64/root/installation-homedir --setenv=HOSTNAME=mock --setenv=PATH=/usr/bin:/bin:/usr/sbin:/sbin --setenv=PROMPT_COMMAND=printf "\033]0;<mock-chroot>\007" --setenv=PS1=<mock-chroot> \s-\v\$  --setenv=LANG=C.UTF-8 --setenv=LC_MESSAGES=C.UTF-8 --resolv-conf=off /usr/bin/dnf --installroot /var/lib/mock/fedora-35-x86_64/root/ --releasever 35 --setopt=deltarpm=False --allowerasing --disableplugin=local --disableplugin=spacewalk --disableplugin=versionlock install @buildsys-build --setopt=tsflags=nocontexts
No matches found for the following disable plugin patterns: local, spacewalk, versionlock
fedora                                               0.0  B/s |   0  B     00:00    
Errors during downloading metadata for repository 'fedora':
  - Curl error (6): Couldn't resolve host name for https://mirrors.fedoraproject.org/metalink?repo=fedora-35&arch=x86_64 [getaddrinfo() thread failed to start]
Error: Failed to download metadata for repo 'fedora': Cannot prepare internal mirrorlist: Curl error (6): Couldn't resolve host name for https://mirrors.fedoraproject.org/metalink?repo=fedora-35&arch=x86_64 [getaddrinfo() thread failed to start]

Additional info:

The mirrors site is resolved OK outside mock.