on IRC someone was reporting that marking a key as trusted does not work.

<binaryplease> muelli: open seahorse, klick right on a key of a friend, properties, trust, tick "your trust of this key" -> https://imgur.com/a/K4rfM
<binaryplease> also this:
<binaryplease> muelli: open seahorse, klick right on a key of a friend, properties, trust, click sign, sign , https://imgur.com/a/IGeXw

The images, if they will be gone, show a rather uninteresting error pop up "Couldn't sign key, General error".

The app prints:
 (seahorse:14324): seahorse-CRITICAL **: file pgp/seahorse-gpgme-key-op.c: line 2420 (photoid_load_transit): should not be reached

When run under GDB the stacktrace indicates a failure to handle a "KEY_CONSIDERED" line that gpg2.1 introduced.

+ Trace 237140

2424        case PHOTO_ID_LOAD_SELECT:
2425            if (status == GPGME_STATUS_GET_LINE && g_str_equal (args, PROMPT)) {
2426                next_state = PHOTO_ID_LOAD_OUTPUT_IMAGE;
2427            } else {
2428                *err = GPG_E (GPG_ERR_GENERAL);
2429                g_return_val_if_reached (PHOTO_ID_LOAD_ERROR);
2430            }
2431            break;