Version 1.15.4 is out. It seems, that upstream again removed the old versions. (also see Bug 663002) >>> Downloading 'https://updates.signal.org/desktop/apt/pool/main/s/signal-desktop/signal-desktop_1.15.2_amd64.deb' --2018-08-13 11:57:35-- https://updates.signal.org/desktop/apt/pool/main/s/signal-desktop/signal-desktop_1.15.2_amd64.deb Resolving updates.signal.org (updates.signal.org)... 52.222.168.27, 52.222.168.142, 52.222.168.45, ... Connecting to updates.signal.org (updates.signal.org)|52.222.168.27|:443... connected. HTTP request sent, awaiting response... 404 Not Found 2018-08-13 11:57:35 ERROR 404: Not Found. !!! Couldn't download 'signal-desktop_1.15.2_amd64.deb'. Aborting. * Fetch failed for 'net-im/signal-desktop-bin-1.15.2', Log file: * '/var/tmp/portage/net-im/signal-desktop-bin-1.15.2/temp/build.log'
Just renaming signal-desktop-bin-1.15.2.ebuild to signal-desktop-bin-1.15.4.ebuild worked for me, 1.15.4 emerged fine.
seems to be fixed in the meantime: https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=1c485dd03e7ab9cb43f5f2f7adb51cd0ff3202c7