Information
The gpgcheck option, found in the main section of the /etc/dnf/dnf.conf and individual /etc/yum.repos.d/* files, determines if an RPM package's signature is checked prior to its installation.
It is important to ensure that an RPM's package signature is always checked prior to installation to ensure that the software is obtained from a trusted source.
Solution
Edit /etc/dnf/dnf.conf and set gpgcheck=1 :
Example
# sed -i 's/^gpgchecks*=s*.*/gpgcheck=1/' /etc/dnf/dnf.conf
Edit any failing files in /etc/yum.repos.d/* and set all instances starting with gpgcheck to 1
Example:
# find /etc/yum.repos.d/ -name "*.repo" -exec echo "Checking:" {} ; -exec sed -i 's/^gpgchecks*=s*.*/gpgcheck=1/' {} ;