Error with apt-get

Recently I tried to update ubuntu software and I got the following error:

dpkg: error processing install-info (--configure):
 subprocess installed post-installation script returned error exit status 1
Errors were encountered while processing:
 install-info

I think it had to do with a resent MySQL update I made. Any way, the only solution that worked for

me was:

sudo mv /var/lib/dpkg/info/install-info.postinst /var/lib/dpkg/info/install-info.postinst.bad

which seems a bit drastic. Oh well, it can be reversed: 

 sudo mv /var/lib/dpkg/info/install-info.postinst.bad /var/lib/dpkg/info/install-info.postinst

 reference: http://ubuntuforums.org/showthread.php?t=1578263 

and update: Similar problem occurred to me when I updated to Ubuntu 16.04. 

/usr/sbin/update-info-dir: 2: /etc/environment: source: not found
dpkg: error processing package install-info (--configure):
 subprocess installed post-installation script returned error exit status 127
Errors were encountered while processing:
 install-info

This time I opened the etc/environment file, and by trial I commented the second line

PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/opt/mysql/server-5.6/bin"
#source /etc/environment  

It worked!