Log Message:
py-notebook: update to 5.2.0

5.2.0
Allow setting token via jupyter_token env.
Fix some errors caused by raising 403 in get_current_user.
Register contents_manager.files_handler_class directly.
Ensure that keyboard shortcuts are disabled when editing them.
Make all files in the dashboard editable by default and provide a whitelist of \ 
viewable file extensions.
The root directory of the notebook server should never be hidden.
Fix notebook require config to match tools/build-main.
Give page constructor default arguments.
Fix codemirror.less to match codemirror's expected padding layout.
Addx-xsrftoken to access-control-allow-headers.
Buffer messages when websocket connection is interrupted.
Load locale dynamically only when not en-us.
Changed key strength to 2048 bits.
Resyncjsversion with python version.
Allow copy operation on modified, read-only notebook.
Update error handling on apihandlers.
Test python 3.6 on travis, drop 3.3.
Avoid base64-literals in image tests.
Upgrade xterm.js to 2.9.2.
Changed all python variables named file to file_name to not override built_in file.
Add more doc tests.
Typos fix.
Rename and update license.
Travis builds doc.
Pull request i18n.
Factor out output_prompt_function, as is done with input prompt.
Use rfc5987 encoding for filenames.
Added path to the resources metadata, the same as in from_filename(...) in \ 
nbconvert.exporters.py.
Make "extrakeys" consistent for notebook and editor.
Bidi support.