When downloading the installer from runescape.com, the file size does not match what is expected. 2017-03-10 09:42:33 (2,11 MB/s) - ‘/usr/portage/distfiles/runescape-launcher_2.2.3_amd64.deb’ saved [2065978/2065978] !!! Fetched file: runescape-launcher_2.2.3_amd64.deb VERIFY FAILED! !!! Reason: Filesize does not match recorded size !!! Got: 2065978 !!! Expected: 2065806 Refetching... File renamed to '/usr/portage/distfiles/runescape-launcher_2.2.3_amd64.deb._checksum_failure_.sOM9Bj' !!! Couldn't download 'runescape-launcher_2.2.3_amd64.deb'. Aborting.
This happens frequently, unfortunately Jagex regularly updates the Ubuntu binary without bumping the package version.
2.2.3 was since dropped: https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=03f20d7a7b3761e06c33c813050814694a4ebc42