test: exception visibility in Python

python_example/maketrees/python/maketrees/__init__.py

@@ -1,6 +1,7 @@
 import tskit
 
 from ._maketrees import maketrees
+from ._maketrees import raise_error
 
 
 def make_treeseq_with_metadata() -> tskit.TreeSequence:

python_example/maketrees/src/lib.rs

@@ -64,4 +64,10 @@ mod maketrees {
         };
         Ok(holder.into_python_tables(py)?)
     }
+
+    #[pyfunction]
+    fn raise_error(py: Python<'_>) -> PyResult<Py<PyAny>> {
+        let holder = tskit2tskit::SharedTableCollection::new(py, f64::NAN)?;
+        Ok(holder.into_python_tables(py)?)
+    }
 }

python_example/maketrees/tests/test_maketrees.py

@@ -21,3 +21,12 @@ def test_metadata():
     ts = maketrees.make_treeseq_with_metadata()
     m = ts.mutation(0).metadata
     assert m['data'] == "I am a mutation"
+
+
+def test_raise():
+    try:
+        _ = maketrees.raise_error()
+    except RuntimeError:
+        pass
+    except _:
+        raise ValueError("expected RuntimeError")