Test TracLegos class and associated functions
=============================================

The imports:

    >>> from pprint import pprint
    >>> from traclegos.legos import sections
    >>> from traclegos.legos import site_configuration
    >>> from traclegos.legos import traclegos_argspec
    >>> from traclegos.legos import TracLegos

Test the constructor argument specification.  This will have to be
changed if TracLegos.__init__ is changed:

    >>> sorted(TracLegos.arguments().keys())
    ['directory', 'inherit', 'master', 'options', 'site_templates', 'vars']

traclegos_argspec should use the left-most non-false value of a list
of dictionaries to provide the arugments to construct TracLegos:

    >>> print repr(traclegos_argspec()['directory'])
    None
    >>> traclegos_argspec({'directory': 'foo'}, {'directory': 'bar'})['directory']
    'bar'
    >>> traclegos_argspec({'directory': 'foo'}, {'directory': None})['directory']
    'foo'

site_configuration should return a dictionary for every section
supported by site-configuration .ini files.  In the case where no
arguments are passed, these should be empty dictionaries:

    >>> set(site_configuration().keys()) == sections
    True