Revert NAScore score to string or None

sciunit/__init__.py

@@ -391,7 +391,7 @@ def judge(self, model, skip_incapable=False, stop_on_error=True,
             try:
                 score = self._judge(model, skip_incapable=skip_incapable)
             except CapabilityError as e:
-                score = NAScore(e)
+                score = NAScore(str(e))
                 score.model = model
                 score.test = self
             except Exception as e:
@@ -973,10 +973,10 @@ class NoneScore(Score):
     checked to see if it has the capabilities required by the test."""
 
     def __init__(self, score, related_data=None):
-        if isinstance(score,(Exception,str)) or score is None:
+        if isinstance(score,str) or score is None:
             super(NoneScore,self).__init__(score, related_data=related_data)
         else:
-            raise InvalidScoreError("Score must be an Exception, a string, or None")
+            raise InvalidScoreError("Score must be a string or None")
 
     @property
     def sort_key(self):