Comment # 3 on bug 1175487 from Sean O'Connell

This problem is not isolated to Spacemacs. I am running Emacs with a bespoke
vanilla config, and encountered the same issue today upon upgrading from
26.3-3.5 to 27.1-1.1 (TW). Further, the problem is not related solely to MELPA
(although I saw the same issues with downloading packages). The error also
presents itself in Elfeed when downloading an enclosure (e.g. a podcast
episode). The download fails with "error in process sentinel: End of file
during parsing". The problem may be related to TLS. The download link that
failed was https. My RSS feeds are a mix of http and https, and Elfeed was able
to pull new articles - however I did not verify if the feeds it successfully
pulled from were http or https.

Rolling back (via snapper), removing ~/.emacs.d/elpa/* and re-running Emacs
26.3-3.5 with the same configuration as prior re-downloaded all packages (via
'use-package' statements) without error. Elfeed downloads worked again, as
well.