readthedocs.org: Install requirements.txt failed ERROR: Exception get_topological_weights assert len(weights) == len(graph

Details

• Read the Docs project URL: https://kashgari.readthedocs.io/en/v2.0.0/
• Build URL (if applicable): https://readthedocs.org/projects/kashgari/builds/12186668/
• Read the Docs username (if applicable): BrikerMan

Expected Result

Build successful

Actual Result

$ /home/docs/checkouts/readthedocs.org/user_builds/kashgari/envs/v2-dev/bin/python -m pip install --use-feature 2020-resolver --exists-action=w --no-cache-dir -r requirements.dev.txt

Downloading parso-0.7.1-py2.py3-none-any.whl (109 kB)
Building wheels for collected packages: pytest-split, m2r, docopt, livereload, tornado, pyrsistent, pandocfilters
  Building wheel for pytest-split (setup.py): started
  Building wheel for pytest-split (setup.py): finished with status 'done'
  Created wheel for pytest-split: filename=pytest_split-0.1.5-py3-none-any.whl size=5646 sha256=4aab47de10ab9b636072c1a272e2a1af8aae634df78d0647d492d35605f3c254
  Stored in directory: /tmp/pip-ephem-wheel-cache-kds2dbfd/wheels/ed/2b/cc/7bc05f351a54d5691bdcbd5be7ed21a30ce7d7e003431aebd7
  Building wheel for m2r (setup.py): started
  Building wheel for m2r (setup.py): finished with status 'done'
  Created wheel for m2r: filename=m2r-0.2.1-py3-none-any.whl size=10466 sha256=254bc68d63d24647591fad8ebffb61f45c00a53af0348ff9dff439f163dc020c
  Stored in directory: /tmp/pip-ephem-wheel-cache-kds2dbfd/wheels/f0/0d/a1/905017ebb11fce6b0316028bf05fc5c4229fbadff0db60182d
  Building wheel for docopt (setup.py): started
  Building wheel for docopt (setup.py): finished with status 'done'
  Created wheel for docopt: filename=docopt-0.6.2-py2.py3-none-any.whl size=13704 sha256=26a64e1d7ecf0cabdcaddb214f360c7b01c71849f13812bcb8ead5c16e53bdbe
  Stored in directory: /tmp/pip-ephem-wheel-cache-kds2dbfd/wheels/56/ea/58/ead137b087d9e326852a851351d1debf4ada529b6ac0ec4e8c
  Building wheel for livereload (setup.py): started
  Building wheel for livereload (setup.py): finished with status 'done'
  Created wheel for livereload: filename=livereload-2.6.3-py2.py3-none-any.whl size=24713 sha256=cf9900c92425363589f03dcdfa18b4613bde017c203ae5e07e8ab619c00330e5
  Stored in directory: /tmp/pip-ephem-wheel-cache-kds2dbfd/wheels/48/d7/34/372e0521bd5c9f6dcdff307e37ef6f9c00c1e1e2afc9707b5c
  Building wheel for tornado (setup.py): started
  Building wheel for tornado (setup.py): finished with status 'done'
  Created wheel for tornado: filename=tornado-6.0.4-cp38-cp38-linux_x86_64.whl size=427572 sha256=0e2641f6aa45412bc5a8e83bf260bfc3689eb152808e583d55c501e1aa7215eb
  Stored in directory: /tmp/pip-ephem-wheel-cache-kds2dbfd/wheels/88/79/e5/598ba17e85eccf2626eab62e4ee8452895636cd542650d450d
  Building wheel for pyrsistent (setup.py): started
  Building wheel for pyrsistent (setup.py): finished with status 'done'
  Created wheel for pyrsistent: filename=pyrsistent-0.17.3-cp38-cp38-linux_x86_64.whl size=119661 sha256=d3d157775d87b7af23707018debb9464602f10d73dbf49beef695bbd6d7f601a
  Stored in directory: /tmp/pip-ephem-wheel-cache-kds2dbfd/wheels/3d/22/08/7042eb6309c650c7b53615d5df5cc61f1ea9680e7edd3a08d2
  Building wheel for pandocfilters (setup.py): started
  Building wheel for pandocfilters (setup.py): finished with status 'done'
  Created wheel for pandocfilters: filename=pandocfilters-1.4.3-py3-none-any.whl size=7991 sha256=a238c3262e1c671d2cf6f981f4f898a638ebe94b945da427bfa8b4ae6529f804
  Stored in directory: /tmp/pip-ephem-wheel-cache-kds2dbfd/wheels/fc/39/52/8d6f3cec1cca4ceb44d658427c35711b19d89dbc4914af657f
Successfully built pytest-split m2r docopt livereload tornado pyrsistent pandocfilters
ERROR: Exception:
Traceback (most recent call last):
  File "/home/docs/checkouts/readthedocs.org/user_builds/kashgari/envs/v2-dev/lib/python3.8/site-packages/pip/_internal/cli/base_command.py", line 228, in _main
    status = self.run(options, args)
  File "/home/docs/checkouts/readthedocs.org/user_builds/kashgari/envs/v2-dev/lib/python3.8/site-packages/pip/_internal/cli/req_command.py", line 182, in wrapper
    return func(self, options, args)
  File "/home/docs/checkouts/readthedocs.org/user_builds/kashgari/envs/v2-dev/lib/python3.8/site-packages/pip/_internal/commands/install.py", line 378, in run
    to_install = resolver.get_installation_order(
  File "/home/docs/checkouts/readthedocs.org/user_builds/kashgari/envs/v2-dev/lib/python3.8/site-packages/pip/_internal/resolution/resolvelib/resolver.py", line 191, in get_installation_order
    weights = get_topological_weights(graph)
  File "/home/docs/checkouts/readthedocs.org/user_builds/kashgari/envs/v2-dev/lib/python3.8/site-packages/pip/_internal/resolution/resolvelib/resolver.py", line 242, in get_topological_weights
    assert len(weights) == len(graph)
AssertionError