Display outputs and errors of command executed with --pipe or `--ch…

…ecks`

#432

CHANGELOG.md

@@ -5,6 +5,8 @@
 - The new jupyterlab extension (in version 1.2.0) is compatible with JupyterLab 2.0. Many thanks to Jean Helie! (#449)
 - It is not compatible with JupyterLab 1.x anymore. If you wish, you can install manually the previous version of the extension with `jupyter labextension install jupyterlab-jupytext@1.1.1`.
 
+**Fixed**
+- Display the output/errors of command executed with `jupytext --pipe` or `jupytext --check` (#432)
 
 1.3.5 (2020-03-08)
 ------------------

jupytext/cli.py

@@ -625,13 +625,18 @@ def exec_command(command, input=None):
     """Execute the desired command, and pipe the given input into it"""
     if not isinstance(command, list):
         command = command.split(' ')
+    sys.stdout.write("[jupytext] Executing {}\n".format(' '.join(command)))
     process = subprocess.Popen(command,
                                **(dict(stdout=subprocess.PIPE, stdin=subprocess.PIPE) if input is not None else {}))
     out, err = process.communicate(input=input)
+    if out:
+        sys.stdout.write(out.decode('utf-8'))
+    if err:
+        sys.stderr.write(err.decode('utf-8'))
 
     if process.returncode:
-        sys.stderr.write("The command {} exited with code {}{}"
-                         .format(command, process.returncode, ': {}'.format(err or out) if err or out else ''))
+        sys.stderr.write("[jupytext] Error: The command '{}' exited with code {}\n"
+                         .format(' '.join(command), process.returncode))
         raise SystemExit(process.returncode)
 
     return out