untar builder fails with error

Greetings,

I"m trying to implement the untar builder from https://github.com/SCons/scons/wiki/UnTarBuilder on scons v3.1.2.bee7caf9defd6e108fc2998a2520ddb36a967691 (ubuntu 20.04)
and I'm getting this error:
AttributeError: 'TarInfo' object has no attribute 'target_peers':
  File "/home/dagg/project/site_scons/build_utils.py", line 471:
    env.Unpack(get_target(), deps_targets_list,
  File "/usr/lib/scons/SCons/Environment.py", line 255:
    return MethodWrapper.__call__(self, target, source, *args, **kw)
  File "/usr/lib/scons/SCons/Environment.py", line 219:
    return self.method(*nargs, **kwargs)
  File "/usr/lib/scons/SCons/Builder.py", line 651:
    return self._execute(env, target, source, OverrideWarner(kw), ekw)
  File "/usr/lib/scons/SCons/Builder.py", line 570:
    t.target_peers = tlist
Compilation failed

has anyone encountered this issue? I cannot seem to be able to find target_peers in reference to python anywhere

the builder looks like this:
import tarfile, os

def message(target, source, env):
    return "Unpacking..."

def builder(target, source, env):
    tar_file = tarfile.open(env['path'])
    tar_file.extractall(env['target'])
    tar_file.close()

    return None

def content_emitter(target, source, env):
    fn = os.path.basename(str(source[0]))
    print("Reading content...")
    tar_file = tarfile.open(str(source[0]), "r")
    new_targets = [ ent for ent in tar_file.getmembers() if ent.isfile() ]
    tar_file.close()
    print("Done")

    return (new_targets, source)

def generate(env, **kwargs):
    unpacker = env.Builder(
        action = env.Action(builder, message),
        src_suffix = ".tar.bz2",
        emitter = content_emitter,
    )

    env.Append(BUILDERS = { 'Unpack' : unpacker })

def exists(env):
    return True

Thanks,

dagg