retitle 56006 "write_wait_fd: unimplemented" during downloading substitutes
thanks

Thiago Jung Bauermann via Bug reports for GNU Guix schreef op wo 15-06-
2022 om 23:40 [-0300]:
> I had a quick look at ‘fetch-narinfos’ but I couldn't figure out what
> could be calling into this unimplemented function ‘write_wait_fd’…

Untested hypothesis: maybe writing to the TLS-wrapped port constructed
in (guix build download) blocked, so Guile's port code ran
'write_wait_fd', which was not set for the TLS port (in the GnuTLS
library)?  Alternatively: maybe 'make-custom-binary-input/output-port'
in (guix build download) was used incorrectly?

Greetings,
Maxime.