Created yum repo will not install on CentOS 5

[raphaelcohn]

Error messages like error: rpmts_HdrFromFdno: Header V3 RSA/SHA1 signature: BAD, key ID 1b9c4af0 are seen, even though the key 1b9c4af0 is installed. This is probably due to an issue with validating RSA signatures in ancient versions of rpm. Apart from using DSA keys (which have other concerns) there doesn't seem to be a realistic workaround.