Look:
root@suore:/home/suore/Downloads# sudo dpkg -i opera-stable_27.0.1689.54_amd64.deb
Selecting previously unselected package opera-stable.
(Reading database ... 393219 files and directories currently installed.)
Preparing to unpack opera-stable_27.0.1689.54_amd64.deb ...
Unpacking opera-stable (27.0.1689.54) ...
Setting up opera-stable (27.0.1689.54) ...
gpg: keyblock resource `/etc/apt/trusted.gpg.d/xorg-edgers-ppa.gpg': resource limit
dpkg: error processing package opera-stable (--install):
subprocess installed post-installation script returned error exit status 2
Processing triggers for mime-support (3.54ubuntu1.1) ...
Processing triggers for gnome-menus (3.10.1-0ubuntu2) ...
Processing triggers for desktop-file-utils (0.22-1ubuntu1) ...
Processing triggers for bamfdaemon (0.5.1+14.04.20140409-0ubuntu1) ...
Rebuilding /usr/share/applications/bamf-2.index...
Processing triggers for hicolor-icon-theme (0.13-1) ...
Errors were encountered while processing:
opera-stable
root@suore:/home/suore/Downloads#
This same problem i have at Opera 26, but i not remember how i resolve it.