Today eix-update (0.35.0) started to crash while writing its database with this message. Subsequent calls to eix result in "error while reading from database: end of file".
there is already a github upstream issue https://github.com/vaeth/eix/issues/87
See https://github.com/vaeth/eix/issues/87#issuecomment-856123869 although I don't think ::guru is using EAPI 8?
eix 0.35.1 does fix the proble for me.
https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=678e157c379c95150d5ab874c1becc5761b19079