How to pip install packages according to requirements.txt from a local directory?

Here is the problem

I have a requirements.txt that looks like:

BeautifulSoup==3.2.0
Django==1.3
Fabric==1.2.0
Jinja2==2.5.5
PyYAML==3.09
Pygments==1.4
SQLAlchemy==0.7.1
South==0.7.3
amqplib==0.6.1
anyjson==0.3
...

I have a local archive directory containing all the packages + others.

I have created a new virtualenv with

bin/virtualenv testing

upon activating it, I tried to install the packages according to requirements.txt from the local archive directory.

source bin/activate
pip install -r /path/to/requirements.txt -f file:///path/to/archive/

I got some output that seems to indicate that the installation is fine

Downloading/unpacking Fabric==1.2.0 (from -r ../testing/requirements.txt (line 3))
  Running setup.py egg_info for package Fabric
    warning: no previously-included files matching '*' found under directory 'docs/_build'
    warning: no files found matching 'fabfile.py'
Downloading/unpacking South==0.7.3 (from -r ../testing/requirements.txt (line 8))
  Running setup.py egg_info for package South
....

But later check revealed none of the package is installed properly. I cannot import the package, and none is found in the site-packages directory of my virtualenv. So what went wrong?