Upgrade attachments CLI cmd: added compatibility with new 'validator' key

We now support both the old coerce=markdown and the new validator=markdown.
Probably support for the old can be removed, but I'm keeping it around
just to be sure.

pillar/cli/maintenance.py

@@ -767,7 +767,9 @@ def iter_markdown(proj_node_types: dict, some_node: dict, callback: typing.Calla
                     continue
                 to_visit.append((subdoc, definition['schema']))
                 continue
-            if definition.get('coerce') != 'markdown':
+            coerce = definition.get('coerce')  # Eve < 0.8
+            validator = definition.get('validator')  # Eve >= 0.8
+            if coerce != 'markdown' and validator != 'markdown':
                 continue
 
             my_log.debug('I have to change %r of %s', key, doc)