refactor: improve python error messages (#2415)

Sometimes, the `setattr` in our special python constructor fails, and
its not so easy to find out why. This should help by printing the key
and the value that did not work together.

Examples/Python/python/acts/_adapter.py

@@ -28,7 +28,12 @@ def wrapped(self, *args, **kwargs):
                 v = str(v)
 
             if hasattr(cfg, k):
-                setattr(cfg, k, v)
+                try:
+                    setattr(cfg, k, v)
+                except TypeError as e:
+                    raise RuntimeError(
+                        "{}: Failed to set {}={}".format(type(cfg), k, v)
+                    ) from e
             else:
                 _kwargs[k] = v
         try: