Sphinx build failing regularly

[oscarbenjamin]

The Sphinx build in CI often fails with:

build finished with problems, 2 warnings.
make[1]: *** [Makefile:69: _html] Error 1
The docs build failed with the following errors:
WARNING: failed to reach any of the inventories with the following issues:
intersphinx inventory 'https://mpmath.org/doc/current/objects.inv' not fetchable due to <class 'requests.exceptions.ConnectionError'>: HTTPSConnectionPool(host='mpmath.org', port=443): Max retries exceeded with url: /doc/current/objects.inv (Caused by NameResolutionError("<urllib3.connection.HTTPSConnection object at 0x7f2d02f7b1a0>: Failed to resolve 'mpmath.org' ([Errno -3] Temporary failure in name resolution)"))
/home/runner/work/sympy/sympy/doc/src/guides/solving/solve-numerically.md:31: WARNING: external py:func reference target not found: mpmath.findroot
make[1]: *** [Makefile:77: printwarnings] Error 1
make: *** [Makefile:58: html] Error 2
Error: Process completed with exit code 2.

It sometimes succeeds so I am not sure what causes the problem. Maybe it is something to do with the mpmath.org server.

[oscarbenjamin]

This seems to have resolved itself.