use pathlib in more places, thereby fixing some bugs

src/c3nav/mapdata/management/commands/clearmapcache.py

@@ -33,7 +33,7 @@ class Command(BaseCommand):
             for filename in os.listdir(settings.CACHE_ROOT):
                 if filename.startswith('history_base_'):
                     logger.info('Deleting %s...' % filename)
-                    os.remove(os.path.join(settings.CACHE_ROOT, filename))
+                    os.remove(settings.CACHE_ROOT / filename)
             logger.info('Base history deleted.')
 
         if not settings.HAS_CELERY and not options['no_process']: