Analyse following RPM build log snippet. Describe contents accurately, without speculation or suggestions for resolution.            
Your analysis must be as concise as possible, while keeping relevant information intact.
Snippet: 
+ sphinx-build docs html
Running Sphinx v8.1.3
WARNING: Invalid configuration value found: 'language = None'. Update your configuration to a valid language code. Falling back to 'en' (English).
loading translations [en]... done
making output directory... done
Converting `source_suffix = '.rst'` to `source_suffix = {'.rst': 'restructuredtext'}`.
ERROR: Invalid value `None` in intersphinx_mapping['https://docs.python.org/']. Expected a two-element tuple or list.
Configuration error:
Invalid `intersphinx_mapping` configuration (1 error).
sphinx failed to generate the documentation.