OCI: dnf(8) Reports Error: "Received HTTP code 403 from proxy after CONNECT"

Applies To:

Oracle Cloud Infrastructure - Version N/A and later
Linux x86-64 on Oracle Public Cloud

Symptoms:

When trying to install packages on an OCI instance, dnf(8) fails with the following error:

Oracle Linux 8 EPEL Packages for Development (x86_64)                                0.0  B/s |   0  B     00:00

Errors during downloading metadata for repository 'ol8_developer_EPEL':

 - Curl error (56): Failure when receiving data from the peer for https://yum-uk-london-1.$ocidomain/repo/OracleLinux/OL8/developer/EPEL/x86_64/repodata/repomd.xml

[Received HTTP code 403 from proxy after CONNECT]

Error: Failed to download metadata for repo 'ol8_developer_EPEL': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried