Add missing location argument to raise
diff --git a/Lib/fontTools/feaLib/builder.py b/Lib/fontTools/feaLib/builder.py
index a164487..0af2f91 100644
--- a/Lib/fontTools/feaLib/builder.py
+++ b/Lib/fontTools/feaLib/builder.py
@@ -1560,7 +1560,8 @@
     def add_conditionset(self, key, value):
         if not "fvar" in self.font:
             raise FeatureLibError(
-                "Cannot add feature variations to a font without an 'fvar' table"
+                "Cannot add feature variations to a font without an 'fvar' table",
+                location=None,
             )
 
         # Normalize