obfs-flash-client incompatible with Twisted 12

In comment:40:ticket:7167, asn reported an error when running obfs-flash-client:

Traceback (most recent call last):
  File "./obfs-flash-client", line 270, in <module>
    sys.exit(main(*sys.argv[1:]))
  File "./obfs-flash-client", line 265, in main
    obfs3_flash(reactor, client, opts.obfs_out, opts.fp_remote)
  File "./obfs-flash-client", line 217, in obfs3_flash
    ["websocket"], [fp_client, '127.0.0.1:%s' % fp_local, fp_remote])
  File "./obfs-flash-client", line 189, in pt_launch_child
    StandardIO(sub_protocol, stdin=sub_proc.stdout.fileno(), reactor=reactor)
TypeError: __init__() got an unexpected keyword argument 'reactor'

I just got the exact same error, running obfs-flash-client with a Twisted from Debian stable, which is version 12. Running with the Twisted from Debian testing (currently 13), I don't get an error. Sure enough, the reactor argument was added between versions 12 and 13:

• http://twistedmatrix.com/documents/12.0.0/api/twisted.internet.stdio.StandardIO.html#init
• http://twistedmatrix.com/documents/13.0.0/api/twisted.internet.stdio.StandardIO.html#init

asn reports that the program works after simply removing the argument. Debian stable is relevant because that's what we are currently using to build the PT bundles.