update exception message

Author: chelsea-lin

bigframes/session/__init__.py

@@ -1053,7 +1053,7 @@ def _read_pandas(
         try:
             return self._read_pandas_load_job(pandas_dataframe, api_name)
         except pa.ArrowInvalid as e:
-            raise pa.ArrowInvalid(f"Unsupported dtype: `{e}`. ")
+            raise pa.ArrowInvalid(f"Could not convert with a BigQuery type: `{e}`. ") from e
 
     def _read_pandas_inline(
         self, pandas_dataframe: pandas.DataFrame
@@ -1068,7 +1068,7 @@ def _read_pandas_inline(
                 blocks.Block.from_local(pandas_dataframe, self)
             )
         except pa.ArrowInvalid as e:
-            raise pa.ArrowInvalid(f"Unsupported dtype: `{e}`. ")
+            raise pa.ArrowInvalid(f"Could not convert with a BigQuery type: `{e}`. ") from e
         except ValueError:  # Thrown by ibis for some unhandled types
             return None
         except pa.ArrowTypeError:  # Thrown by arrow for types without mapping (geo).

tests/system/small/test_session.py

@@ -438,7 +438,7 @@ def test_read_pandas_index(session):
 
 
 def test_read_pandas_w_unsupported_mixed_dtype(session):
-    with pytest.raises(pa.ArrowInvalid, match="Unsupported dtype"):
+    with pytest.raises(pa.ArrowInvalid, match="Could not convert"):
         session.read_pandas(pd.DataFrame({"a": [1, "hello"]}))