python NameError: name 'file' is not defined
It seems that your project is written in Python < 3. This is because the file() builtin function is removed in Python 3. Try using Python 2to3 tool or edit the erroneous file yourself.
EDIT: BTW, the project page clearly mentions that
Gunicorn requires Python 2.x >= 2.5. Python 3.x support is planned.
file is not defined in Python3, which you are using apparently. The package you're instaling is not suitable for Python 3, instead, you should install Python 2.7 and try again.
See: http://docs.python.org/release/3.0/whatsnew/3.0.html#builtins