Problem with python3.8: pickle / multiprocessing problem

[jenisys]

Current versions 0.1.17, 0.1.18 and HEAD cause a problem if you install wstool with python 3.8.

HOW-TO-REPEAT:

$ git clone https://github.com/vcstools/wstool.git
$ cd wstool
$ python --version
Python 3.8.0
$ pip install .
...
Successfully installed wstool-0.1.18

$ cd .../into_directory_with_rosinstall_file
$ wstool
Traceback (most recent call last):
  File "/xxx/.venv_py38/bin/wstool", line 62, in <module>
    sys.exit(wstool.wstool_cli.wstool_main(sys.argv))
  File "/xxx/.venv_py38/lib/python3.8/site-packages/wstool/wstool_cli.py", line 185, in wstool_main
    return ws_commands[command](workspace, args)
  File "/xxx/.venv_py38/lib/python3.8/site-packages/wstool/multiproject_cli.py", line 1286, in cmd_info
    outputs = multiproject_cmd.cmd_info(config,
  File "/xxx/.venv_py38/lib/python3.8/site-packages/wstool/multiproject_cmd.py", line 545, in cmd_info
    outputs = work.run()
  File "/xxx/.venv_py38/lib/python3.8/site-packages/wstool/common.py", line 352, in run
    self.threads[i].start()
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/multiprocessing/process.py", line 121, in start
    self._popen = self._Popen(self)
    ...
    File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/multiprocessing/popen_fork.py", line 19, in __init__
    self._launch(process_obj)
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/multiprocessing/popen_spawn_posix.py", line 47, in _launch
    reduction.dump(process_obj, fp)
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/multiprocessing/reduction.py", line 60, in dump
    ForkingPickler(file, protocol).dump(obj)
AttributeError: Can't pickle local object 'cmd_info.<locals>.InfoRetriever'

NOTE: Same version of wstool works in python 2.7.16 and python 3.7.x without any problems.

[dirk-thomas]

Closing since the repository is about to be archived: see #154.