install python package "poster"

It's quite simple, you can use easy_install or pip, in your terminal run:

easy_install poster

or

pip install poster

If you don't have easy_install or pip, install distribute first:

curl -O http://python-distribute.org/distribute_setup.py
python distribute_setup.py

I recommend using pip and reading the excellent documentation. You might also benefit from reading the python documentation about distributing modules.

In the future search pypi. If it's on pypi you can pip or easy_install it.

reference:

http://stackoverflow.com/questions/5906878/installing-posterstreaming-http-uploads-and-multipart-form-data-encoding