it was oracle-java8* from ppa:webupd8team/java ... even ppa-purge had trouble handling them. do-release-upgrade should handle these situations or at least tell what packages are causing the problem.
$ sudo ppa-purge -p java webupd8team Updating packages lists PPA to be removed: webupd8team java Package revert list generated: oracle-java8-installer/trusty oracle-java8-set-default/trusty Disabling webupd8team PPA from /etc/apt/sources.list.d/webupd8team-java-trusty.list Updating packages lists Reading package lists... Done Building dependency tree Reading state information... Done E: Release 'trusty' for 'oracle-java8-installer' was not found E: Release 'trusty' for 'oracle-java8-set-default' was not found Unable to find an archive "trusty" for the package "oracle-java8-installer" Unable to find an archive "trusty" for the package "oracle-java8-set-default" Unable to find an archive "trusty" for the package "oracle-java8-installer" Unable to find an archive "trusty" for the package "oracle-java8-set-default" No packages will be installed, upgraded, or removed. 0 packages upgraded, 0 newly installed, 0 to remove and 1 not upgraded. Need to get 0 B of archives. After unpacking 0 B will be used. PPA purged successfully using aptitude fallback $ sudo ppa-purge -p java webupd8team Updating packages lists PPA to be removed: webupd8team java Warning: Could not find package list for PPA: webupd8team java $ dpkg -l | grep oracle ii oracle-java8-installer 8u66+8u65arm-1~webupd8~1 all Oracle Java(TM) Development Kit (JDK) 8 ii oracle-java8-set-default 8u66+8u65arm-1~webupd8~1 all Set Oracle JDK 8 as default Java $ sudo apt-get remove --purge oracle-java8-installer oracle-java8-set-default Reading package lists... Done Building dependency tree Reading state information... Done The following packages will be REMOVED: oracle-java8-installer* oracle-java8-set-default* 0 upgraded, 0 newly installed, 2 to remove and 1 not upgraded. After this operation, 167 kB disk space will be freed. Do you want to continue? [Y/n] (Reading database ... 239897 files and directories currently installed.) Removing oracle-java8-set-default (8u66+8u65arm-1~webupd8~1) ... Purging configuration files for oracle-java8-set-default (8u66+8u65arm-1~webupd8~1) ... Removing oracle-java8-installer (8u66+8u65arm-1~webupd8~1) ... -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1512819 Title: do-release-upgrade refused to upgrade 14.04 to vivid To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/ubuntu-release-upgrader/+bug/1512819/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs