The allow_trusted argument gets lost during a install_files call. The python backend crashes with the following stacktrace:

Error Type:
Error Value: list index out of range
File : /usr/share/PackageKit/helpers/apt/aptBackend.py, line 2201, in
main()
File : /usr/share/PackageKit/helpers/apt/aptBackend.py, line 2198, in main
run(args, options.single)
File : /usr/share/PackageKit/helpers/apt/aptBackend.py, line 2160, in run
backend.dispatcher(args)
File : /usr/lib/python2.6/dist-packages/packagekit/backend.py, line 699, in dispatcher
self.dispatch_command(args[0], args[1:])
File : /usr/lib/python2.6/dist-packages/packagekit/backend.py, line 590, in dispatch_command
files_to_inst = args[1].split(FILENAME_DELIM)
 CancelOk

The corresponding output of packagekitd:
TI:09:50:36FI:pk-store.cFN:pk_store_set_strv,90
 - saving 0x85fd558 for full_paths
TI:09:50:36FI:pk-backend-spawn.c FN:pk_backend_spawn_helper_va_list,715
 - using spawn filename /usr/share/PackageKit/helpers/apt/aptBackend.py
TI:09:50:36FI:pk-backend-spawn.c FN:pk_backend_spawn_get_envp,608
 - setting evp 'LANG=en_US.utf8'
TI:09:50:36FI:pk-network-stack-nm.c FN:pk_network_stack_nm_get_active_connection_type,202
 - active connections: 1
TI:09:50:36FI:pk-network-stack-nm.c FN:pk_network_stack_nm_get_active_connection_type_for_connection,133
 - is_default: 1
TI:09:50:36FI:pk-network-stack-nm.c FN:pk_network_stack_nm_get_active_connection_type_for_connection,153
 - number of devices: 1
TI:09:50:36FI:pk-network-stack-nm.c FN:pk_network_stack_nm_get_active_connection_type_for_device,93
 - type: 1
TI:09:50:36FI:pk-network-stack-nm.c FN:pk_network_stack_nm_get_state,251
 - network state is wired
TI:09:50:36FI:pk-backend-spawn.c FN:pk_backend_spawn_get_envp,616
 - setting evp 'NETWORK=TRUE'
TI:09:50:36FI:pk-backend-spawn.c FN:pk_backend_spawn_get_envp,622
 - setting evp 'IDLE=FALSE'
TI:09:50:36FI:pk-spawn.c FN:pk_spawn_argv,448
 - argv[0] '/usr/share/PackageKit/helpers/apt/aptBackend.py'
TI:09:50:36FI:pk-spawn.c FN:pk_spawn_argv,448
 - argv[1] 'install-files'
TI:09:50:36FI:pk-spawn.c FN:pk_spawn_argv,448
 - argv[2] '/tmp/xterm_243-1ubuntu1_i386.deb'
TI:09:50:36FI:pk-spawn.c FN:pk_spawn_argv,452
 - envp[0] 'LANG=en_US.utf8'
TI:09:50:36FI:pk-spawn.c FN:pk_spawn_argv,452
 - envp[1] 'NETWORK=TRUE'
TI:09:50:36FI:pk-spawn.c FN:pk_spawn_argv,452
 - envp[2] 'IDLE=FALSE'
TI:09:50:36FI:pk-spawn.c FN:pk_spawn_argv,502
 - creating new instance of /usr/share/PackageKit/helpers/apt/aptBackend.py
TI:09:50:36FI:pk-spawn.c FN:pk_spawn_argv,530
 - setting ioprio class to idle
TI:09:50:36FI:pk-backend-spawn.c FN:pk_backend_spawn_parse_stdout,467
 - invalid command 'Error: No BACKGROUND envp'
TI:09:50:36FI:pk-transaction.c FN:pk_transaction_status_changed_emit,437
 - emitting status-changed 'loading-cache'
TI:09:50:36FI:pk-transaction.c FN:pk_transaction_status_changed_emit,441
 - emitting changed
TI:09:50:36FI:pk-transaction-list.c FN:pk_transaction_list_is_consistent,734
 - checking consistency as length 1
TI:09:50:36FI:pk-transaction-list.c FN:pk_transaction_list_print,702
 - State:
0simulate-install-files/46_bcbbbcae_datarunning[1] committed[1] finished[0] background[0]

TI:09:50:37FI:pk-transaction.c FN:pk_transaction_error_code_emit,465
 - emitting error-code internal-error, 'Error Type: <type 'exceptions.IndexError'>
Error Value: list index out of range
  File : /usr/share/PackageKit/helpers/apt/aptBackend.py, line 2203, in <module>
    main()
  File : /usr/share/PackageKit/helpers/apt/aptBackend.py, line 2200, in main
    run(args, options.single)
  File : /usr/share/PackageKit/helpers/apt/aptBackend.py, line 2162, in run
    backend.dispatcher(args)
  File : /usr/lib/python2.6/dist-packages/packagekit/backend.py, line 699, in dispatcher
    self.dispatch_command(args[0], args[1:])
  File : /usr/lib/python2.6/dist-packages/packagekit/backend.py, line 590, in dispatch_command
    files_to_inst = args[1].split(FILENAME_DELIM)
'
TI:09:50:37FI:pk-backend.c FN:pk_backend_finished,1954
 - finished role unknown
TI:09:50:37FI:pk-transaction.c FN:pk_transaction_allow_cancel_cb,478
 - emitting allow-cancel 0
TI:09:50:37FI:pk-transaction.c FN:pk_transaction_status_changed_emit,437
 - emitting status-changed 'finished'
TI:09:50:37FI:pk-transaction.c FN:pk_transaction_status_changed_emit,441
 - emitting changed
TI:09:50:37FI:pk-backend.c FN:pk_backend_finished,2015
 - adding finished 0x85b2800 to timeout loop
TI:09:50:37FI:pk-spawn.c FN:pk_spawn_check_child,228
 - Running fork failed with return value 1
TI:09:50:37FI:pk-spawn.c FN:pk_spawn_check_child,252
 - emitting exit failed
TI:09:50:37FI:pk-backend-spawn.c FN:pk_backend_spawn_exit_cb,491
 - script exited without doing finished
TI:09:50:37FI:pk-backend.c FN:pk_backend_finished,1954
 - finished role unknown
TI:09:50:37FI:pk-backend.c FN:pk_backend_finished,1965
 - already finished