Comment 15 for bug 1236951

Update from 13.10 to 14.04 caused me this problem too: the upgrade failed to
install tex-common and emacsen-common and reinstalling did not work.
Combining the comments above with instructions on
http://tug.org/texlive/
this is what worked for me.
If someone can say how this should really be done, I'd be happy to see it.

1. Uninstall everything to do with emacs and xemacs
(I used synaptic package manager, to find what to remove and to completely remove)

2. Uninstall tex-common and all texlive-* files and

sudo rm -rf /etc/texmf

as in comment 12 above.

3. Remove all texlive files (if any) e.g.

sudo rm -rf /usr/local/texlive/2014
rm -rf ~/.texlive2014

4. Install emacs24 then auctex using synaptic package manager

5. Install tex-common using synaptic package manager

6. Install texlive following the instructions on http://tug.org/texlive/
(Installation from dpkg or Ubuntu software centre or synaptic package manager don't work for me.)

7. Add paths to /etc/environment as suggested by the installation program in 6.
That is, for the version I installed,
to the end of the PATH line add

:/usr/local/texlive/2014/bin/x86_64-linux

just before the closing"
and add 2 new lines

INFOPATH=":/usr/local/texlive/2014/texmf-dist/doc/info"
MANPATH=":/usr/local/texlive/2014/texmf-dist/doc/man"

(without the colon, the manpath to everything except tex will be broken)

8. Edit /etc/manpath.config
by adding line

MANPATH_MAP /usr/local/texlive/2014/bin/x86_64-linux /usr/local/texlive/2014/texmf-dist/doc/man

after the last MANPATH_MAP line that already exists.