fix some bugs in code change

return notebook object instead of raw string

let user choose how to deal with execution result.

let user choose how to deal with execution result.

let user choose how to deal with execution result.

update max_worker back

add output_path

update execute.py

update execute.py

papermill/execute.py

@@ -136,7 +136,7 @@ def log_outputs(cell):
 
 
 def execute_notebook(notebook,
-                     output=None,
+                     output,
                      parameters=None,
                      kernel_name=None,
                      progress_bar=True,
@@ -151,8 +151,8 @@ def execute_notebook(notebook,
         progress_bar (bool): Flag for whether or not to show the progress bar.
         log_output (bool): Flag for whether or not to write notebook output to stderr.
     """
-    # print("Input Notebook:  %s" % get_pretty_path(notebook))
-    # print("Output Notebook: %s" % get_pretty_path(output))
+    print("Input Notebook:  %s" % get_pretty_path(notebook))
+    print("Output Notebook: %s" % get_pretty_path(output))
     nb = load_notebook_node(notebook)
 
     # Parameterize the Notebook.
@@ -182,10 +182,10 @@ def execute_notebook(notebook,
     nb.metadata.papermill['exception'] = any(
         [cell.metadata.papermill.get('exception') for cell in nb.cells])
 
-    if output:
-        # Write final Notebook to disk.
-        write_ipynb(nb, output)
-        raise_for_execution_errors(nb, output)
+    # Write final Notebook to disk.
+    write_ipynb(nb, output)
+    raise_for_execution_errors(nb, output)
+    # always return notebook object
     return nb