This is rather strange. what does "port -d extract" give ?
white:~ root# port -d extract py-cairo
DEBUG: Changing to port directory: /opt/local/var/db/dports/sources/rsync.rsync.darwinports.org_dpupdate_dports/python/py-cairo
DEBUG: Requested variant powerpc is not provided by port py-cairo.
DEBUG: Requested variant darwin is not provided by port py-cairo.
DEBUG: Requested variant macosx is not provided by port py-cairo.
DEBUG: Skipping completed com.apple.main (py-cairo)
DEBUG: Skipping completed com.apple.fetch (py-cairo)
DEBUG: Skipping completed com.apple.checksum (py-cairo)
DEBUG: Skipping completed com.apple.extract (py-cairo)
w