Update changelog for version 15

9 jobs for v15 in 12 minutes and 8 seconds (queued for 2 minutes and 33 seconds)
Name Stage Failure
linkcheck Build
(line  391) ok        https://healpy.readthedocs.io/en/stable/generated/healpy.pixelfunc.ud_grade.html#healpy.pixelfunc.ud_grade
(line 391) ok https://healpy.readthedocs.io/en/stable/generated/healpy.pixelfunc.get_interp_val.html#healpy.pixelfunc.get_interp_val
(line 391) ok https://healpy.readthedocs.io/en/stable/tutorial.html
(line 16) ok https://healpix.jpl.nasa.gov/images/healpixGridRefinement.jpg
(line 420) broken https://doi.org/10.1111/j.1365-2966.2007.12297.x - ('Connection aborted.', OSError("(104, 'ECONNRESET')"))

build finished with problems, 3 warnings.
WARNING: Not copying tabs assets! Not compatible with linkcheck builder
ERROR: Job failed: exit code 1