python3-opencv not found on rhel:8 during bloom release

[Kenji Brameld]

During bloom release, python3-opencv is not found on rhel:8. This is not an issue in this repo, but should be fixed in rosdistro. This happens on galactic, humble and rolling.

Output of bloom:

Pre-verifying RPM dependency keys...
Running 'rosdep update'...
Could not resolve rosdep key 'python3-opencv' for distro '8':
No definition of [python3-opencv] for OS [rhel]
        rosdep key : python3-opencv
        OS name    : rhel
        OS version : 8
        Data:
debian:
                - python3-opencv
                fedora:
                - python3-opencv
                gentoo:
                - media-libs/opencv[python]
                nixos:
                - python3Packages.opencv3
                openembedded:
                - opencv@meta-oe
                opensuse:
                - python3-opencv
                ubuntu:
                - python3-opencv

Failed to resolve python3-opencv on rhel:8 with: Error running generator: Failed to resolve rosdep key 'python3-opencv', aborting.
python3-opencv is depended on by these packages: ['cv_bridge']
<== Failed
Some of the dependencies for packages in this repository could not be resolved by rosdep.
<== The following generator action reported that it is missing one or more
    rosdep keys, but that the key exists in other platforms:
'['/usr/bin/git-bloom-generate', '-y', 'rosrpm', '--prefix', 'release/rolling', 'rolling', '-i', '1', '--os-name', 'rhel']'

If you are absolutely sure that this key is unavailable for the platform in
question, the generator can be skipped and you can proceed with the release.
Skip generator action and continue with release [y/N]? y

Action skipped, continuing with release.