family.py: Do not use the `imp` module in Python 3
family.py: Do not use the `imp` module in Python 3

The `imp` module is deprecated since version 3.4 in favor of importlib.
Use `sys.path.append` and `importlib.import_module` instead of
`imp.load_source`.

Bug: T158640
Change-Id: Id12c9e991a2d359afdbd7f7e29558282ff39c5cb

jayvdb/pywikibot-core,wikimedia/pywikibot-core,Darkdadaah/pywikibot-core,hasteur/g13bot_tools_new,magul/pywikibot-core,jayvdb/pywikibot-core,magul/pywikibot-core,hasteur/g13bot_tools_new,npdoty/pywikibot,npdoty/pywikibot,happy5214/pywikibot-core,hasteur/g13bot_tools_new,Darkdadaah/pywikibot-core,PersianWikipedia/pywikibot-core,wikimedia/pywikibot-core,happy5214/pywikibot-core