def METHOD_NAME(args, project, package, nsource):
    if nsource is None:
        nsource = ''
    file_path = "{0}/{1}/{1}.spec".format(project, package)
    for line in obs_get_file(args, file_path).split('\n'):
        source = match('^Source{}:\s*(.+)$'.format(nsource), line)
        if source:
            return source.group(1)