Returns the name of the main application from the given ini file parser.
    The name is found as follows:
     * If the ini file contains only one app:<app name> section,
       return this app name;
     * Else, if the ini file contains a pipeline:main section, use
       the name of the innermost app;
     * Else raise ValueError.

    :param ini_parser: :class:`configparser.SafeConfigParser` instance with
        an ini file read.

def app_name_from_ini_parser(ini_parser):
    """
    Returns the name of the main application from the given ini file parser.
    The name is found as follows:
     * If the ini file contains only one app:<app name> section,
       return this app name;
     * Else, if the ini file contains a pipeline:main section, use
       the name of the innermost app;
     * Else raise ValueError.

    :param ini_parser: :class:`configparser.SafeConfigParser` instance with
        an ini file read.
    """
    app_names = [sect.split(':')[-1]
                 for sect in ini_parser.sections()
                 if sect[:4] == 'app:']
    if len(app_names) == 1:
        app_name = app_names[0]
    else:
        pp_sect_name = 'pipeline:main'
        if ini_parser.has_section(pp_sect_name):
            pipeline_apps = ini_parser.get(pp_sect_name, 'pipeline').split()
            app_name = pipeline_apps[-1]
        else:
            raise ValueError('Could not determine application name. '
                             'You need to either define exactly one '
                             'app:<app name> section or a '
                             'pipeline:main section in your ini '
                             'file.')
    return app_name