fix error type regression

Author: TrevorBergeron

bigframes/core/blocks.py

@@ -278,7 +278,7 @@ def resolve_label_exact_or_error(self, label: Label) -> str:
         raises an error. If there is no such a column, raises an error too."""
         col_id = self.resolve_label_exact(label)
         if col_id is None:
-            raise KeyError(f"Label {label} not found. {constants.FEEDBACK_LINK}")
+            raise ValueError(f"Label {label} not found. {constants.FEEDBACK_LINK}")
         return col_id
 
     @functools.cached_property

bigframes/dataframe.py

@@ -3010,7 +3010,9 @@ def agg(
             funcnames = []
             for col_label, agg_func in func.items():
                 agg_func_list = agg_func if utils.is_list_like(agg_func) else [agg_func]
-                col_id = self._block.resolve_label_exact_or_error(col_label)
+                col_id = self._block.resolve_label_exact(col_label)
+                if col_id is None:
+                    raise KeyError(f"Column {col_label} does not exist")
                 for agg_func in agg_func_list:
                     agg_op = agg_ops.lookup_agg_func(typing.cast(str, agg_func))
                     agg_expr = (