"bzr log bzr+ssh://bazaar.launchpad.net/~jml/testtools/trunk/README" fails with PermissionDenied

Here's what I get when I try to "bzr log" an individual file in a branch hosted on bazaar.launchpad.net:

$ bzr log bzr+ssh://bazaar.launchpad.net/~jml/testtools/trunk/README
bzr: ERROR: Server sent an unexpected error: ('error', 'Permission denied: "Cannot create \'README\'. Only Bazaar branches are allowed."')

$ bzr log sftp://bazaar.launchpad.net/~jml/testtools/trunk/README
bzr: ERROR: Permission denied: "/~jml/testtools/trunk/README/.bzr/branch-format": [Errno 13] Permission denied: "Cannot create 'README'. Only Bazaar branches are allowed."

$ bzr log http://bazaar.launchpad.net/~jml/testtools/trunk/README
bzr: ERROR: No such file: 'http://bazaar.launchpad.net/~jml/testtools/trunk/README'

In contrast, here's what I expect, based on what happens with a regular OpenSSH SFTP server and bzr 1.9 install:

$ bzr log sftp://localhost/~/code/testtools/trunk/README | head -3
andrew@localhost's password:
------------------------------------------------------------
revno: 11
committer: Jonathan Lange <email address hidden>

$ bzr log bzr+ssh://localhost/home/andrew/code/testtools/trunk/README | head -3
andrew@localhost's password:
------------------------------------------------------------
revno: 11
committer: Jonathan Lange <email address hidden>

$ bzr log http://localhost:8080/code/testtools/trunk/README | head -3
------------------------------------------------------------
revno: 11
committer: Jonathan Lange <email address hidden>