Upgrade fails with Faraday::ConnectionFailed: proxy connection could not be established (Excon::Error::ProxyConnectionError)

Issue

• Upgrading Satellite from 6.9 to 6.10 fails in step "Switching specified content over to pulp 3"

• satellite-maintain upgrade --target-version=6.10 fails with following error

  2022-11-10 10:59:13 +0100: Importing migrated yum repositories: 2501/2511
  Content Migration completed successfully
  Performing a check to verify everything that is needed has been migrated
  
  Switching specified content over to pulp 3                            [FAIL]
  Failed executing foreman-rake katello:pulp3_content_switchover, exit status 1:
   rake aborted!
  Faraday::ConnectionFailed: proxy connection could not be established (Excon::Error::ProxyConnectionError)
  /opt/theforeman/tfm/root/usr/share/gems/gems/excon-0.76.0/lib/excon/ssl_socket.rb:115:in `initialize'
  /opt/theforeman/tfm/root/usr/share/gems/gems/excon-0.76.0/lib/excon/connection.rb:465:in `new'
  /opt/theforeman/tfm/root/usr/share/gems/gems/excon-0.76.0/lib/excon/connection.rb:465:in `socket'
  /opt/theforeman/tfm/root/usr/share/gems/gems/excon-0.76.0/lib/excon/connection.rb:118:in `request_call'
  /opt/theforeman/tfm/root/usr/share/gems/gems/excon-0.76.0/lib/excon/middlewares/mock.rb:57:in `request_call'
  /opt/theforeman/tfm/root/usr/share/gems/gems/excon-0.76.0/lib/excon/middlewares/instrumentor.rb:34:in `request_call'
  /opt/theforeman/tfm/root/usr/share/gems/gems/excon-0.76.0/lib/excon/middlewares/idempotent.rb:19:in `request_call'
  ...