New items are already in the map (for deleted + renamed)

I note the diff from the bzr branch that created the revision:

rm bb/gpg.py
mv aa/gpg.py bb/gpg.py
diff of bb/gpg.py

svn 1.4 server's revision diff looks like this:

diff of bb/gpg.py (delta between aa/gpg.py and bb/gpg.py)
diff of aa/gpg.py (deleting all lines)

When I attempt to recreate with a modern svn (1.6.12) repository, the svn diff looks the same, but the bzr/bzr-svn head (or current release) bzr diff looks like this:

mv aa/gpg.py bb/gpg.py
diff bb/gpg.py
rm bb/gpg.py

(note that the order is different, and would seem to be saying that it is deleting the bb/gpg.py file (though the end result is correct)).

With bzr/bzr-svn head pushing into an svn 1.4 server, I get the "you need file revision properties enabled" warning when trying to recreate the issue, but with that enabled the whole process succeeds, so possibly we are no longer producing the confusing file properties, but we still seem to crash if they are already in the repository (even when checking out with head of bzr and bzr-svn).

This is beginning to look like a problem with the file-property-stored revision metadata? Is the traceback trying to tell me that the metadata for the filename bb/gpg.py has already been added to the mapping because we aren't properly handling the duplicate bb/gpg.py file-metadata property set? IIUC what's happening is we're likely pulling the file rev-props out and assuming that the file-path will be unique when we go to add them to the mapping?