how fix this error on fedora 26 ?!
Code:
[root@localhost sajjad]# dnf install libX11-devel libxml2-devel libxslt-devel freetype-devel flex bison SFML SFML-devel openal-soft-devel ffmpeg-libs
Error: Failed to synchronize cache for repo 'updates'
[root@localhost sajjad]# dnf check-update --refresh
Error: Failed to synchronize cache for repo 'updates'
[root@localhost sajjad]# dnf-deprecated update
bash: dnf-deprecated: command not found
[root@localhost sajjad]# dnf clean all
5 files removed
[root@localhost sajjad]# dnf clean all
0 files removed
[root@localhost sajjad]# dnf distro-sync --refresh
Copr repo for persepolis owned by amirsamimi 1.6 kB/s | 2.0 kB     00:01    
Error: Failed to synchronize cache for repo 'updates'
[root@localhost sajjad]# dnf update
Fedora 26 - x86_64 - Updates                  23 kB/s | 9.9 MB     07:26    
Error: Failed to synchronize cache for repo 'fedora'
[root@localhost sajjad]# dnf install libX11-devel libxml2-devel libxslt-devel freetype-devel flex bison SFML SFML-devel openal-soft-devel ffmpeg-libs
Error: Failed to synchronize cache for repo 'fedora'
[root@localhost sajjad]# dnf install openssl openvpn mod_ssl easy-rsa -y
Error: Failed to synchronize cache for repo 'fedora'
[root@localhost sajjad]# exit
exit
[sajjad@localhost ~]$