Don't import notebook when jupyter_server is available

Author: mwouts

CHANGELOG.md

@@ -7,6 +7,9 @@ Jupytext ChangeLog
 **Changed**
 - We have updated the pre-commit hooks. The code is now formatted using `ruff format`, and updated for Python 3.9+ using https://github.com/asottile/pyupgrade ([#1423](https://github.com/mwouts/jupytext/issues/1423))
 
+**Fixed**
+- We don't import `notebook` when `jupyter_server` is available ([#1436](https://github.com/mwouts/jupytext/issues/1436))
+
 
 1.17.3 (2025-08-28)
 -------------------

src/jupytext/async_contentsmanager.py

@@ -18,12 +18,6 @@
 import nbformat
 from tornado.web import HTTPError
 
-# import notebook.transutils before notebook.services.contents.filemanager #75
-try:
-    import notebook.transutils  # noqa
-except ImportError:
-    pass
-
 from .async_pairs import read_pair, write_pair
 from .config import (
     JUPYTEXT_CONFIG_FILES,
@@ -681,7 +675,13 @@ def _drop_formats_if_they_dont_match_path(self, path, fmt, formats):
 
     AsyncTextFileContentsManager = build_async_jupytext_contents_manager_class(AsyncLargeFileManager)
 except ImportError:
-    # If we can't find jupyter_server then we take it from notebook
+    # If we can't find jupyter_server then we take the file manager from notebook
+    # import notebook.transutils needs to happen before notebook.services.contents.filemanager, see #75
+    try:
+        import notebook.transutils  # noqa
+    except ImportError:
+        pass
+
     try:
         from notebook.services.contents.largefilemanager import AsyncLargeFileManager
 

src/jupytext/sync_contentsmanager.py

@@ -24,12 +24,6 @@
 import nbformat
 from tornado.web import HTTPError
 
-# import notebook.transutils before notebook.services.contents.filemanager #75
-try:
-    import notebook.transutils  # noqa
-except ImportError:
-    pass
-
 from .sync_pairs import read_pair, write_pair
 from .config import (
     JUPYTEXT_CONFIG_FILES,
@@ -760,7 +754,13 @@ def _drop_formats_if_they_dont_match_path(self, path, fmt, formats):
         LargeFileManager
     )
 except ImportError:
-    # If we can't find jupyter_server then we take it from notebook
+    # If we can't find jupyter_server then we take the file manager from notebook
+    # import notebook.transutils needs to happen before notebook.services.contents.filemanager, see #75
+    try:
+        import notebook.transutils  # noqa
+    except ImportError:
+        pass
+
     try:
         from notebook.services.contents.largefilemanager import LargeFileManager