Find all non-builtins import in a python project

About

- we use `ack` (`ack-grep`)
- we assume builtins are marked so, or in a `python*` directory in a `lib` one, but not in `*packages*` (`site-packages for example`)
- everything that cannot be imported is not a builtin package

If your python is not in a "lib/pythonX.Y" directory, you can change the path.

PS: on my machine, it works in a virtualenv

find-packages.sh

ack --py '^\s*(from [^.][^"\s]+\s)?import' -h |  sed -r 's/^\s+//' |sed -r ' s/^(from|import) (\w+).*/\2/' | sort | uniq | xargs python -c "
import sys, imp
for mod in sys.argv[1:]:
    try:
        res = imp.find_module(mod)
    except:
        print(mod)
    else:
        if res[2][2] != imp.C_BUILTIN and ('lib/python' not in res[1] or 'packages' in res[1]):
            print(mod)
"