Merge pull request #6285 from theotherjimmy/fix-6284

Improve json schema and schema errors

Author: cmonr

tools/config/__init__.py

@@ -392,7 +392,7 @@ def format_validation_error(self, error, path):
             return self.format_validation_error(error.context[0], path)
         else:
             return "in {} element {}: {}".format(
-                path, str(".".join(error.absolute_path)), error.message)
+                path, str(".".join(str(p) for p in error.absolute_path)), error.message)
 
     def __init__(self, tgt, top_level_dirs=None, app_config=None):
         """Construct a mbed configuration

tools/config/definitions.json

@@ -11,7 +11,7 @@
     "type": "array",
     "items": {
       "type": "string",
-      "pattern": "(^[\\w]+$|^[\\w]+=.+$)"
+      "pattern": "(^[\\w()_]+$|^[\\w()_]+=.+$)"
     }
   },
   "config_definition": {