Cannot upgrade to latest version (4.0.9) MacOS

[edevil]

What were you doing?

Upgrade to the latest version which supposedly solves another problem I'm having.

What did you expect to happen?

Upgrade completes.

What happened instead?

2019-10-01 12:17:02,203 - octoprint.plugins.softwareupdate - ERROR - Update of octoprint can not be performed
Traceback (most recent call last):
  File "/Users/andre/BEESOFT4/BEEweb/src/octoprint/plugins/softwareupdate/__init__.py", line 923, in _perform_update
    update_result = updater.perform_update(target, populated_check, target_version, log_cb=self._log)
  File "/Users/andre/BEESOFT4/BEEweb/src/octoprint/plugins/softwareupdate/updaters/update_script.py", line 88, in perform_update
    caller.checked_call(update_command, cwd=folder)
  File "/Users/andre/BEESOFT4/BEEweb/src/octoprint/util/commandline.py", line 66, in checked_call
    returncode, stdout, stderr = self.call(command, **kwargs)
  File "/Users/andre/BEESOFT4/BEEweb/src/octoprint/util/commandline.py", line 83, in call
    p = sarge.run(command, **kwargs)
  File "build/bdist.macosx-10.4-x86_64/egg/sarge/__init__.py", line 1462, in run
    p.run(input=input, async_=async_)
  File "build/bdist.macosx-10.4-x86_64/egg/sarge/__init__.py", line 1071, in run
    self.run_node(node, input=input, async_=False)
  File "build/bdist.macosx-10.4-x86_64/egg/sarge/__init__.py", line 1187, in run_node
    result = getattr(self, method)(node, input, async_)
  File "build/bdist.macosx-10.4-x86_64/egg/sarge/__init__.py", line 1333, in run_command_node
    node.cmd.run(input=input, async_=async_)
  File "build/bdist.macosx-10.4-x86_64/egg/sarge/__init__.py", line 655, in run
    self.process = p = Popen(self.args, **self.kwargs)
TypeError: __init__() got an unexpected keyword argument 'async'

Branch & Commit or Version of OctoPrint

4.0.8

Operating System running OctoPrint

MacOS 10.14.6