Why does yum/dnf and reposync fails with error "Received HTTP code 407 from proxy after CONNECT" ?

Issue

• The reposync fails on the system behind proxy and following error occurs.

  # reposync -p <download-path> --download-metadata --repo=<repo id>
  .
  .
  [FAILED] insights-client-3.1.7-7.el8_6.noarch.rpm: No more mirrors to try - All mirrors were already tried without success
  [MIRROR] perl-Text-Diff-1.44-3.module+el8+2464+d274aed1.noarch.rpm: Curl error (56): Failure when receiving data from the peer for https://cdn.redhat.com/content/dist/rhel8/8/x86_64/appstream/os/Packages/p/perl-Text-Diff-1.44-3.module%2bel8%2b2464%2bd274aed1.noarch.rpm [Received HTTP code 407 from proxy after CONNECT]
  [MIRROR] bpg-sans-regular-fonts-1.005-10.el8.noarch.rpm: Curl error (56): Failure when receiving data from the peer for https://cdn.redhat.com/content/dist/rhel8/8/x86_64/appstream/os/Packages/b/bpg-sans-regular-fonts-1.005-10.el8.noarch.rpm [Received HTTP code 407 from proxy after CONNECT]
  [FAILED] bpg-sans-regular-fonts-1.005-10.el8.noarch.rpm: No more mirrors to try - All mirrors were already tried without success
  [FAILED] perl-Text-Diff-1.44-3.module+el8+2464+d274aed1.noarch.rpm: No more mirrors to try - All mirrors were already tried without success
  

• The yum/dnf fails on the system behind proxy and following error occurs.

   # yum list updates
  Updating Subscription Management repositories.
  Red Hat Satellite Maintenance 6.12 for RHEL 8 x86_64 (RPMs)                                                                                         0.0  B/s |   0  B     00:00
  Errors during downloading metadata for repository 'satellite-maintenance-6.12-for-rhel-8-x86_64-rpms':
    - Curl error (56): Failure when receiving data from the peer for https://cdn.redhat.com/content/dist/layered/rhel8/x86_64/sat-maintenance/6.12/os/repodata/repomd.xml [Received HTTP code 407 from proxy after CONNECT]
  Error: Failed to download metadata for repo 'satellite-maintenance-6.12-for-rhel-8-x86_64-rpms': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried