If you're using the one-click full install of OpenERP you will see that with "pip install unidecode" won't work. That's because the one-click install comes with its own python packages.

So you need to download the zipped file from: https://pypi.python.org/pypi/Unidecode

Then you need to unzip it and copy the "unicode" folder and paste it into the /Server/server/ folder. In my case OpenERP v7 is installed in, c:\Program Files (x86)\OpenERP 7.0-20130412-232402\Server\server

Restart the server and that's it :)

Today is Apr 27, 2023 and after trying a lot of things, the answer of Eric from 2014 was the one that worked for me. I downloaded the  "Unidecode-1.3.6.tar.gz" file from https://pypi.org/project/Unidecode/#files. Then I unzipped the file and got a folder called "Unidecode-1.3.6". Inside that I found all the files and a folder called "unidecode". I copied that folder and just pasted it in my server folder where the odoo-bin and odoo.conf files are located. Restarted the server and "Update Apps List" on the Odoo platform (Developer mode on). I installed the module that was having the error and it worked perfectly! No errors. Thanks Eric.

Answers of Eric and Andres Rojas works for me as well.

To do this on docker, login the bash

pip3 install unidecode

restart your container 

with ubuntu

sudo apt-get install python-unicodecsv

and restart the server