Make traceback a getter

Author: jakubno

js/src/messaging.ts

@@ -25,7 +25,7 @@ export class ExecutionError {
   /**
    * Returns the traceback of the error as a string.
    */
-  traceback(): string {
+  get traceback(): string {
     return this.tracebackRaw.join('\n')
   }
 }

python/tests/test_streaming.py

@@ -4,9 +4,11 @@
 def test_streaming_output():
     out = []
     with CodeInterpreter() as sandbox:
+
         def test(line) -> int:
             out.append(line)
             return 1
+
         sandbox.notebook.exec_cell("print(1)", on_stdout=test)
 
     assert len(out) == 1
@@ -16,7 +18,9 @@ def test(line) -> int:
 def test_streaming_error():
     out = []
     with CodeInterpreter() as sandbox:
-        sandbox.notebook.exec_cell("import sys;print(1, file=sys.stderr)", on_stderr=out.append)
+        sandbox.notebook.exec_cell(
+            "import sys;print(1, file=sys.stderr)", on_stderr=out.append
+        )
 
     assert len(out) == 1
     assert out[0].line == "1\n"
@@ -41,4 +45,3 @@ def test_streaming_result():
         sandbox.notebook.exec_cell(code, on_result=out.append)
 
     assert len(out) == 2
-