agent plugin fails to detect correct file injection capability

Using nova bzr 1269 with Xenserver. I'm creating instances using a Squeeze image with nova-agent 0.0.1.28 installed.

When I create a new instance and try to inject a file I get the following error in /var/log/nova/nova-agent.log:

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2011-07-14 13:24:22,552 [INFO] Received command 'file_inject' with argument: '{'b64_file': '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', 'b64_path': 'L3Jvb3QvLnNzaC9hdXRob3JpemVkX2tleXM='}'
2011-07-14 13:24:22,553 [WARNING] No such agent command 'file_inject'
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In nova-compute.log I see the following:

2011-07-14 13:24:17,063 DEBUG nova.virt.xenapi.vmops [-] Injecting file path: '/root/.ssh/authorized_keys' from (pid=6569) _inject_files /usr/lib/pymodules/python2.6/nova/virt/xenapi/vmops.py:320
2011-07-14 13:24:20,243 INFO nova.virt.xenapi [-] Task [Async.host.call_plugin] OpaqueRef:fc1a875e-f609-97a4-42fb-e664df556d37 status: success <value>&quot;{\&quot;message\&quot;: \&quot;No such agent command 'file_inject'\&quot;, \&quot;returncode\&quot;: \&quot;404\&quot;}&quot;</value>
2011-07-14 13:24:20,250 WARNING nova.virt.xenapi.vmops [-] string indices must be integers
2011-07-14 13:24:20,251 ERROR nova.virt.xenapi.vmops [-] Instance instance-00000017: failed to boot
(nova.virt.xenapi.vmops): TRACE: Traceback (most recent call last):
(nova.virt.xenapi.vmops): TRACE: File "/usr/lib/pymodules/python2.6/nova/virt/xenapi/vmops.py", line 341, in _wait_for_boot
(nova.virt.xenapi.vmops): TRACE: _inject_files()
(nova.virt.xenapi.vmops): TRACE: File "/usr/lib/pymodules/python2.6/nova/virt/xenapi/vmops.py", line 321, in _inject_files
(nova.virt.xenapi.vmops): TRACE: self.inject_file(instance, path, contents)
(nova.virt.xenapi.vmops): TRACE: File "/usr/lib/pymodules/python2.6/nova/virt/xenapi/vmops.py", line 706, in inject_file
(nova.virt.xenapi.vmops): TRACE: if resp_dict['returncode'] != '0':
(nova.virt.xenapi.vmops): TRACE: TypeError: string indices must be integers
(nova.virt.xenapi.vmops): TRACE:

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I looks like the Xenserver agent plugin isn't detecting the correct file injection method for instances.