Tracking of imported names
==========================

We have an AST walker that keeps track of scopes and names used in
expressions

    >>> from findimports import find_imports_and_track_names

    >>> open('marmalade.py', 'w').write('''
    ... import sys, os
    ... my_name_is = sys.argv[0]
    ... ''')

    >>> imports, unused_names = find_imports_and_track_names('marmalade.py')
    >>> for imp in imports:
    ...     print imp
    ImportInfo('sys', 'marmalade.py', 2)
    ImportInfo('os', 'marmalade.py', 2)

    >>> for name in unused_names:
    ...     print name
    ImportInfo('os', 'marmalade.py', 2)

