Seahorse fails to import private PGP keys: pinentry-gtk-2 passphrase prompt not displayed

to reproduce this :

create a PGP key with seahorse (4096-bits)
export the private key in .asc format and delete the original key
then try to import it from seahorse.

the importation fails with this error :

keyserver option ‘ce-cert-filv’ is unknown

Feature Branch: bugfix/12733-seahorse-vs-pinentry-gtk2

Original created by @goupille on 12733 (Redmine)

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