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.
Rationale:
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 in the [main] section.
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/' {} ;