Update Fedora 31 : When I try to upgrade Fedora 30 to Fedora 31, I get this error: 

Copr repo for wpa_supplicant owned by dcaratti  4.2 kB/s | 3.3 kB     00:00    
Fedora Modular 30 - x86_64                       28 kB/s |  24 kB     00:00    
Fedora Modular 30 - x86_64 - Updates             38 kB/s |  23 kB     00:00    
Fedora 30 - x86_64 - Updates                     76 kB/s |  22 kB     00:00    
Fedora 30 - x86_64                               29 kB/s |  25 kB     00:00    
google-chrome                                    16 kB/s | 1.3 kB     00:00    
PostgreSQL 12 for Fedora 30 - x86_64            5.2 kB/s | 3.8 kB     00:00    
PostgreSQL 11 for Fedora 30 - x86_64            5.0 kB/s | 3.8 kB     00:00    
PostgreSQL 10 for Fedora 30 - x86_64             11 kB/s | 3.8 kB     00:00    
PostgreSQL 9.6 for Fedora 30 - x86_64            13 kB/s | 3.8 kB     00:00    
PostgreSQL 9.5 for Fedora 30 - x86_64           6.2 kB/s | 3.8 kB     00:00    
PostgreSQL 9.4 for Fedora 30 - x86_64            11 kB/s | 3.8 kB     00:00    
RPM Fusion for Fedora 30 - Free - Updates        16 kB/s | 9.6 kB     00:00    
RPM Fusion for Fedora 30 - Free                  38 kB/s |  10 kB     00:00    
RPM Fusion for Fedora 30 - Nonfree - Updates     17 kB/s | 9.8 kB     00:00    
RPM Fusion for Fedora 30 - Nonfree               42 kB/s |  11 kB     00:00    
skype (stable)                                  9.1 kB/s | 2.9 kB     00:00    
Error: 
 Problem: The operation would result in removing the following protected packages: dnf
(try to add '--skip-broken' to skip uninstallable packages)

How I can it fixed? Thanks.