system_hotkey was written for a previous version of Python that had
collections.Iterable available. That moved under collections.abc in a
later release.

--- a/system_hotkey/system_hotkey.py
+++ b/system_hotkey/system_hotkey.py
@@ -281,7 +281,7 @@ class MixIn():
 
         thread safe
         '''
-        assert isinstance(hotkey, collections.Iterable) and type(hotkey) not in (str, bytes)
+        assert isinstance(hotkey, collections.abc.Iterable) and type(hotkey) not in (str, bytes)
         if self.consumer == 'callback' and not callback:
             raise TypeError('Function register requires callback argument in non sonsumer mode')