Running Sphinx v3.5.0
Loading template...
Finding news fragments...
Rendering news fragments...
Draft only -- nothing has been written.
What is seen below is what would be written.

loading translations [en]... done

Traceback (most recent call last):
  File "/home/docs/checkouts/readthedocs.org/user_builds/tox/envs/1920/lib/python3.6/site-packages/sphinx/cmd/build.py", line 279, in build_main
    args.tags, args.verbosity, args.jobs, args.keep_going)
  File "/home/docs/checkouts/readthedocs.org/user_builds/tox/envs/1920/lib/python3.6/site-packages/sphinx/application.py", line 245, in __init__
    self.setup_extension(extension)
  File "/home/docs/checkouts/readthedocs.org/user_builds/tox/envs/1920/lib/python3.6/site-packages/sphinx/application.py", line 402, in setup_extension
    self.registry.load_extension(self, extname)
  File "/home/docs/checkouts/readthedocs.org/user_builds/tox/envs/1920/lib/python3.6/site-packages/sphinx/registry.py", line 417, in load_extension
    mod = import_module(extname)
  File "/home/docs/checkouts/readthedocs.org/user_builds/tox/envs/1920/lib/python3.6/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 994, in _gcd_import
  File "<frozen importlib._bootstrap>", line 971, in _find_and_load
  File "<frozen importlib._bootstrap>", line 955, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 665, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 674, in exec_module
  File "<frozen importlib._bootstrap_external>", line 781, in get_code
  File "<frozen importlib._bootstrap_external>", line 741, in source_to_code
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/home/docs/checkouts/readthedocs.org/user_builds/tox/envs/1920/lib/python3.6/site-packages/sphinxcontrib/autoprogram.py", line 11
    from __future__ import annotations
                                     ^
SyntaxError: future feature annotations is not defined

Exception occurred:
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/home/docs/checkouts/readthedocs.org/user_builds/tox/envs/1920/lib/python3.6/site-packages/sphinxcontrib/autoprogram.py", line 11
    from __future__ import annotations
                                     ^
SyntaxError: future feature annotations is not defined