`ModuleNotFoundError: No module named 'six'` on build

Details

I tried building my docs for my project, yet this fails with a ModuleNotFoundError

My conf file Build url

Expected Result

A successful build

Actual Result

The following error:

Running Sphinx v3.3.1

Traceback (most recent call last):
  File "/home/docs/checkouts/readthedocs.org/user_builds/dblstats/envs/latest/lib/python3.7/site-packages/sphinx/config.py", line 319, in eval_config_file
    execfile_(filename, namespace)
  File "/home/docs/checkouts/readthedocs.org/user_builds/dblstats/envs/latest/lib/python3.7/site-packages/sphinx/util/pycompat.py", line 89, in execfile_
    exec(code, _globals)
  File "/home/docs/checkouts/readthedocs.org/user_builds/dblstats/checkouts/latest/docs/source/conf.py", line 82, in <module>
    from six import string_types
ModuleNotFoundError: No module named 'six'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/home/docs/checkouts/readthedocs.org/user_builds/dblstats/envs/latest/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/docs/checkouts/readthedocs.org/user_builds/dblstats/envs/latest/lib/python3.7/site-packages/sphinx/application.py", line 219, in __init__
    self.config = Config.read(self.confdir, confoverrides or {}, self.tags)
  File "/home/docs/checkouts/readthedocs.org/user_builds/dblstats/envs/latest/lib/python3.7/site-packages/sphinx/config.py", line 174, in read
    namespace = eval_config_file(filename, tags)
  File "/home/docs/checkouts/readthedocs.org/user_builds/dblstats/envs/latest/lib/python3.7/site-packages/sphinx/config.py", line 332, in eval_config_file
    raise ConfigError(msg % traceback.format_exc()) from exc
sphinx.errors.ConfigError: There is a programmable error in your configuration file:

Traceback (most recent call last):
  File "/home/docs/checkouts/readthedocs.org/user_builds/dblstats/envs/latest/lib/python3.7/site-packages/sphinx/config.py", line 319, in eval_config_file
    execfile_(filename, namespace)
  File "/home/docs/checkouts/readthedocs.org/user_builds/dblstats/envs/latest/lib/python3.7/site-packages/sphinx/util/pycompat.py", line 89, in execfile_
    exec(code, _globals)
  File "/home/docs/checkouts/readthedocs.org/user_builds/dblstats/checkouts/latest/docs/source/conf.py", line 82, in <module>
    from six import string_types
ModuleNotFoundError: No module named 'six'


Configuration error:
There is a programmable error in your configuration file:

Traceback (most recent call last):
  File "/home/docs/checkouts/readthedocs.org/user_builds/dblstats/envs/latest/lib/python3.7/site-packages/sphinx/config.py", line 319, in eval_config_file
    execfile_(filename, namespace)
  File "/home/docs/checkouts/readthedocs.org/user_builds/dblstats/envs/latest/lib/python3.7/site-packages/sphinx/util/pycompat.py", line 89, in execfile_
    exec(code, _globals)
  File "/home/docs/checkouts/readthedocs.org/user_builds/dblstats/checkouts/latest/docs/source/conf.py", line 82, in <module>
    from six import string_types
ModuleNotFoundError: No module named 'six'

[arunhpatil]

Hi, I had the same issue. At first, I followed the recommendation https://github.com/readthedocs/readthedocs.org/issues/7704#issuecomment-735030431 but it was not complete without specifying requirements in the settings.

Solved

Here is how I solved it, first follow https://github.com/readthedocs/readthedocs.org/issues/7704#issuecomment-735030431, and then click Admin, Advanced Settings and then under the section Requirements file add the file path you created docs/requirements.txt. Click on Save and build Version. I hope this works out for you.

Cheers.

[humitos]

Hi all! I deployed a quick fix for now that does not install latest sphinx version by default (3.3.1) but the previous one that Read the Docs pinned for years (1.8.x).

We enabled this feature (USE_LATEST_SPHINX for new projects) to start testing the builder with this new version of Sphinx, but we didn’t realize that six was not a dependency anymore. So, for now, I disabled this feature and your builds will use sphinx==1.8.x by default. If you want to use a different version of Sphinx, please specify it in your requirements.txt file as usual.

We will have a fix for this soon and we will re-enable USE_LATEST_SPHINX version for new projects.