Hi!
While rebuilding the python related packages against the Python 3.15rc2
version we found that jupyter-server-terminals fails to build from
source:
https://debusine.debian.net/debian/r-python-python3.15/artifact/4855869/
There are several errors in log, similar to this one:
----------------------------- Captured stderr call
-----------------------------
[W 2026-09-24 22:37:39.281 TerminalsExtensionApp] wrote error:
'Unhandled error'
[E 2026-09-24 22:37:39.281 TerminalsExtensionApp] {
"Host": "127.0.0.1:38553",
"User-Agent": "Tornado/6.5.5"
}
[E 2026-09-24 22:37:39.281 TerminalsExtensionApp] 500 POST
/a%40b/api/terminals (f9185ef712b7464faeec794057ab41fc@127.0.0.1) 4.33ms
referer=None
------------------------------ Captured log call
-------------------------------
[35mDEBUG [0m ServerApp:identity.py:499 Accepting
token-authenticated request from 127.0.0.1
[35mDEBUG [0m TerminalsExtensionApp:identity.py:530 Generating new
user for token-authenticated request: f9185ef712b7464faeec794057ab41fc
[35mDEBUG [0m TerminalsExtensionApp:api_handlers.py:60 Opening
terminal in:
/tmp/pytest-of-sbuild/pytest-0/test_terminal_create_with_cwd0/terminal_path
[31m[1mERROR [0m ServerApp:web.py:1966 Uncaught exception POST
/a%40b/api/terminals (127.0.0.1)
HTTPServerRequest(protocol='http', host='127.0.0.1:38553',
method='POST', uri='/a%40b/api/terminals', version='HTTP/1.1',
remote_ip='127.0.0.1')
Traceback (most recent call last):
File "/usr/lib/python3/dist-packages/tornado/web.py", line 1880, in
_execute
result = await result
^^^^^^^^^^^^
File
"/usr/lib/python3/dist-packages/jupyter_server/auth/decorator.py", line
71, in inner
out = method(self, *args, **kwargs)
File
"/build/reproducible-path/jupyter-server-terminals-0.5.3/.pybuild/cpython3_3.15/build/jupyter_server_terminals/api_handlers.py",
line 63, in post
model = self.terminal_manager.create(**data)
File
"/build/reproducible-path/jupyter-server-terminals-0.5.3/.pybuild/cpython3_3.15/build/jupyter_server_terminals/terminalmanager.py",
line 51, in create
name, term = self.new_named_terminal(**kwargs)
~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^
File "/usr/lib/python3/dist-packages/terminado/management.py", line
404, in new_named_terminal
term = self.new_terminal(**kwargs)
File "/usr/lib/python3/dist-packages/terminado/management.py", line
233, in new_terminal
return PtyWithClients(argv, env, cwd)
File "/usr/lib/python3/dist-packages/terminado/management.py", line
58, in __init__
self.ptyproc = PtyProcessUnicode.spawn(**kwargs)
~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^
File "/usr/lib/python3/dist-packages/ptyprocess/ptyprocess.py", line
230, in spawn
pid, fd = pty.fork()
~~~~~~~~^^
File "/usr/lib/python3.15/pty.py", line 66, in fork
pid, fd = os.forkpty()
~~~~~~~~~~^^
DeprecationWarning: This process (pid=101) is multi-threaded, use of
forkpty() may lead to deadlocks in the child.
[33mWARNING [0m TerminalsExtensionApp:handlers.py:779 wrote error:
'Unhandled error'
[31m[1mERROR [0m TerminalsExtensionApp:log.py:106 {
"Host": "127.0.0.1:38553",
"User-Agent": "Tornado/6.5.5"
}
[31m[1mERROR [0m TerminalsExtensionApp:log.py:107 500 POST
/a%40b/api/terminals (f9185ef712b7464faeec794057ab41fc@127.0.0.1) 4.33ms
referer=None
Please note that while we ran into this error during the rebuild against
Python 3.15, that doesn't mean that the root cause for the failure is
necessarily the new Python version.
Setting the severity to important for now. Once Python 3.15 is released
and later added to python3-defaults, this bug will become release
critical.