"port -d selfupdate" failure with latest MacOS & Xcode

[John Wiggins]

Using Xcode 16.4 with Command Line Tools for Xcode 16.4 on M1 Mac mini running macOS Sequoia 15.5 the self update gives the following error:

MacPorts base version 2.10.7 installed,
MacPorts base version 2.10.7 available.
DEBUG: Rebuilding and reinstalling MacPorts if needed
--->  MacPorts base is already the latest version
--->  Updating the ports tree
Synchronizing local ports tree from rsync://rsync.macports.org/macports/release/tarballs/ports.tar
DEBUG: system: /usr/bin/rsync -rtzvl --delete-after --include=/ports.tar.gz --include=/ports.tar.gz.rmd160 --exclude=* rsync://rsync.macports.org/macports/release/tarballs/ /opt/local/var/macports/sources/rsync.macports.org/macports/release/tarballs/remote
Willkommen auf dem RSYNC-server auf ftp.fau.de.
Nicht all unsere Mirror sind per rsync verfuegbar.
Welcome to the RSYNC daemon on ftp.fau.de.
Not all of our mirrors are available through rsync.
rsync: [sender] change_dir "/release/tarballs" (in macports) failed: Permission denied (13)
rsync(1647): warning: receiver has empty file list: exiting
Command failed: /usr/bin/rsync -rtzvl --delete-after --include=/ports.tar.gz --include=/ports.tar.gz.rmd160 --exclude=* rsync://rsync.macports.org/macports/release/tarballs/ /opt/local/var/macports/sources/rsync.macports.org/macports/release/tarballs/remote
Exit code: 23
Error: Synchronization of the local ports tree failed doing rsync
DEBUG: Couldn't sync the ports tree: Synchronization of 1 source failed
    while executing
"error "Couldn't sync the ports tree: $eMessage""
    (procedure "do_sync" line 15)
    invoked from within
"do_sync $options 0"
    (procedure "selfupdate::main" line 100)
    invoked from within
"selfupdate::main {ports_no_migration_check 1 options_selfupdate_order {} options_global_order {}} selfupdate_status"
    ("uplevel" body line 1)
    invoked from within
"uplevel [list selfupdate::main $options $updatestatusvar]"
    (procedure "macports::selfupdate" line 2)
    invoked from within
"macports::selfupdate $options selfupdate_status"
Error: Couldn't sync the ports tree: Synchronization of 1 source failed
Error: Follow https://guide.macports.org/#project.tickets if you believe there is a bug.
Error: /opt/local/bin/port: port selfupdate failed: Couldn't sync the ports tree: Synchronization of 1 source failed