Return all known local groups to the system.

def _get_local_groups(self):
        '''
        Return all known local groups to the system.
        '''
        groups = dict()
        path = '/etc/group'
        with salt.utils.files.fopen(path, 'r') as fp_:
            for line in fp_:
                line = line.strip()
                if ':' not in line:
                    continue
                name, password, gid, users = line.split(':')
                groups[name] = {
                    'gid': gid,
                }

                if users:
                    groups[name]['users'] = users.split(',')

        return groups