build: report errors a little better in download_gha_artifacts.py
build: report errors a little better in download_gha_artifacts.py

nedbat/coveragepy,hugovk/coveragepy,hugovk/coveragepy,hugovk/coveragepy,nedbat/coveragepy,hugovk/coveragepy,hugovk/coveragepy,nedbat/coveragepy,nedbat/coveragepy,nedbat/coveragepy