Given following log snippets, their explanation, and nothing else, explain what failure, if any, occurred during build of this package.

  Snippets are in a format of [X] : [Y], where [X] is a log snippet, and [Y] is the explanation.

  Snippets are delimited with '================'.

  Drawing on information from all snippets, provide a concise explanation of the issue and recommend a solution.

  Explanation of the issue, and recommended solution, should take a handful of sentences.

  Snippets:

  [ERROR: Invalid value `None` in intersphinx_mapping['https://docs.python.org/3/']. Expected a two-element tuple or list.
Configuration error:
Invalid `intersphinx_mapping` configuration (1 error).]: [Error message]

Issue: Project documentation as configured is not buildable with sphinx of this version.
Resolution: Fix the documentation configuration either by changing the source code or by adding a patch with fix.