Feature Request: Show build durations using sphinx.ext.duration

Details

• Read the Docs project URL: https://readthedocs.org/projects/astropy/
• Build URL (if applicable): https://readthedocs.org/projects/astropy/builds/12314499/
• Read the Docs username (if applicable): pllim

This is a follow-up from https://github.com/readthedocs/readthedocs.org/issues/7648#issuecomment-724953115 .

cc @saimn and @humitos

Expected Result

When sphinx.ext.duration (which has been available since Sphinx 2.4 and we are using 3.x) is enabled by adding it to extensions list in conf.py, we expect an output like this in the build log:

====================== slowest reading durations =======================
16.173 coordinates/index
14.260 visualization/wcsaxes/ticks_labels_grid
12.112 visualization/rgb
11.582 visualization/wcsaxes/overlays
9.496 timeseries/index
7.912 stats/ripley
6.881 visualization/wcsaxes/slicing_datacubes
...
1.543 modeling/example-fitting-line
1.494 timeseries/io

Actual Result

“slowest reading durations” isn’t shown. ~I don’t have that commit to prove this anymore, but I will recreate it and link it back here.~ See astropy/astropy#11028

[saimn]

Hmm weird, since it works locally (for astropy). Not sure what could cause a difference on RTD.

[pllim]

Well, don’t have to remove that label so soon, bot.