Ввод «n» в вопрос aptitude заставит его предложить другое решение - понизить некоторые пакеты. Это сработало для меня!
Accept this solution? [Y/n/q/?] n
The following actions will resolve these dependencies:
Downgrade the following packages:
1) libexpat1 [2.1.0-4ubuntu1.3 (now) -> 2.1.0-4ubuntu1 (trusty)]
2) libpython2.7 [2.7.6-8ubuntu0.3 (now) -> 2.7.6-8 (trusty)]
3) libpython2.7-minimal [2.7.6-8ubuntu0.3 (now) -> 2.7.6-8 (trusty)]
4) libpython2.7-stdlib [2.7.6-8ubuntu0.3 (now) -> 2.7.6-8 (trusty)]
5) python2.7 [2.7.6-8ubuntu0.3 (now) -> 2.7.6-8 (trusty)]
6) python2.7-minimal [2.7.6-8ubuntu0.3 (now) -> 2.7.6-8 (trusty)]
Accept this solution? [Y/n/q/?] y