Detect execution errors earlier, avoiding the unhelpful "attempting to execute an unsuccessful or closed pending query result" errors (#41)

This PR fixes duckdb/duckdb#18106

Author: evertlammerts

src/duckdb_py/pyconnection.cpp

@@ -465,6 +465,9 @@ shared_ptr<DuckDBPyConnection> DuckDBPyConnection::ExecuteMany(const py::object
 
 unique_ptr<QueryResult> DuckDBPyConnection::CompletePendingQuery(PendingQueryResult &pending_query) {
 	PendingExecutionResult execution_result;
+	if (pending_query.HasError()) {
+		pending_query.ThrowError();
+	}
 	while (!PendingQueryResult::IsResultReady(execution_result = pending_query.ExecuteTask())) {
 		{
 			py::gil_scoped_acquire gil;

tests/fast/udf/test_remove_function.py

@@ -52,7 +52,7 @@ def func(x: int) -> int:
             Error: Catalog Error: Scalar Function with name func does not exist!
         """
         with pytest.raises(
-            duckdb.InvalidInputException, match='Attempting to execute an unsuccessful or closed pending query result'
+            duckdb.CatalogException, match='Scalar Function with name func does not exist!'
         ):
             res = rel.fetchall()
 
@@ -72,7 +72,7 @@ def also_func(x: int) -> int:
             return x
 
         con.create_function('func', also_func)
-        with pytest.raises(duckdb.InvalidInputException, match='No function matches the given name'):
+        with pytest.raises(duckdb.BinderException, match='No function matches the given name'):
             res = rel2.fetchall()
 
     def test_overwrite_name(self):
@@ -98,7 +98,7 @@ def other_func(x):
         con.remove_function('func')
 
         with pytest.raises(
-            duckdb.InvalidInputException, match='Catalog Error: Scalar Function with name func does not exist!'
+            duckdb.CatalogException, match='Catalog Error: Scalar Function with name func does not exist!'
         ):
             # Attempted to execute the relation using the 'func' function, but it was deleted
             rel1.fetchall()