Macports fails under Sierra?

[Dave Horsfall]

Upgraded recently to 10.12 Sierra, and "port upgrade" now fails:

    Welcome to the RSYNC daemon on ftp.fau.de.
    Not all of our mirrors are available through rsync.


    receiving file list ... done
    rsync: mkstemp "/opt/local/var/macports/sources/rsync.macports.org/release/tarballs/.base.tar.sH7E8E" failed: Permission denied (13)
    inflate returned -3 (19 bytes)
    rsync error: error in rsync protocol data stream (code 12) at /BuildRoot/Library/Caches/com.apple.xbs/Sources/rsync/rsync-51/rsync/token.c(419) [receiver=2.6.9]
    rsync: connection unexpectedly closed (31 bytes received so far) [generator]
    rsync error: error in rsync protocol data stream (code 12) at /BuildRoot/Library/Caches/com.apple.xbs/Sources/rsync/rsync-51/rsync/io.c(453) [generator=2.6.9]
    Command failed: /usr/bin/rsync -rtzv --delete-after rsync://rsync.macports.org/release/tarballs/base.tar 
    /opt/local/var/macports/sources/rsync.macports.org/release/tarballs Exit code: 12
    Error: Error synchronizing MacPorts sources: command execution failed
    To report a bug, follow the instructions in the guide:
        http://guide.macports.org/#project.tickets
    Error: /opt/local/bin/port: port selfupdate failed: Error synchronizing MacPorts sources: command execution failed

Yet the directory exists, and is certainly writable by root:

    ls -ld /opt/local/var/macports/sources/rsync.macports.org/release/tarballs

    drwxr-xr-x  5 root  admin  170 Sep 26 06:12 /opt/local/var/macports/sources/rsync.macports.org/release/tarballs

Qué?

-- 
Dave Horsfall DTM (VK2KFU)  "Those who don't understand security will suffer."