Does not work with sphinx 3.5.1

[truenicoco]

# Sphinx version: 3.5.1
# Python version: 3.7.3 (CPython)
# Docutils version: 0.16 release
# Jinja2 version: 2.11.3
# Last messages:

# Loaded extensions:
Traceback (most recent call last):
  File "/home/nicoco/.cache/pypoetry/virtualenvs/pysignald-async-E_E3_Jap-py3.7/lib/python3.7/site-packages/sphinx/cmd/build.py", line 279, in build_main
    args.tags, args.verbosity, args.jobs, args.keep_going)
  File "/home/nicoco/.cache/pypoetry/virtualenvs/pysignald-async-E_E3_Jap-py3.7/lib/python3.7/site-packages/sphinx/application.py", line 245, in __init__
    self.setup_extension(extension)
  File "/home/nicoco/.cache/pypoetry/virtualenvs/pysignald-async-E_E3_Jap-py3.7/lib/python3.7/site-packages/sphinx/application.py", line 402, in setup_extension
    self.registry.load_extension(self, extname)
  File "/home/nicoco/.cache/pypoetry/virtualenvs/pysignald-async-E_E3_Jap-py3.7/lib/python3.7/site-packages/sphinx/registry.py", line 430, in load_extension
    metadata = setup(app)
  File "/home/nicoco/.cache/pypoetry/virtualenvs/pysignald-async-E_E3_Jap-py3.7/lib/python3.7/site-packages/m2r.py", line 652, in setup
    app.add_source_parser('.md', M2RParser)
  File "/home/nicoco/.cache/pypoetry/virtualenvs/pysignald-async-E_E3_Jap-py3.7/lib/python3.7/site-packages/sphinx/application.py", line 1204, in add_source_parser
    self.registry.add_source_parser(parser, override=override)
  File "/home/nicoco/.cache/pypoetry/virtualenvs/pysignald-async-E_E3_Jap-py3.7/lib/python3.7/site-packages/sphinx/registry.py", line 267, in add_source_parser
    for filetype in parser.supported:
AttributeError: 'str' object has no attribute 'supported'

[vazhnov]

Is it the same issue as here https://github.com/CrossNox/m2r2/issues/13 ?

[truenicoco]

Definitely looks like it.

[arwedus]

this extension seems to be abandoned by @miyakogi