x/build: LUCI swarming bot works with Python 3.13 but not Python 3.14 due to reliance on removed pkgutil.get_loader

[n2vi]

Go version

I use go1.27rc1 there, but this is probably not about Go. Python reports 3.14.4.

Output of go env in your module/workspace:

not relevant?

What did you do?

I tried to start the builder as usual.

What did you see happen?

2026/06/28 18:16:31 Downloading the swarming bot 2026/06/28 18:16:33 Starting the swarming bot /home/swarming/.swarming/swarming_bot.zip Traceback (most recent call last): File "", line 198, in _run_module_as_main File "", line 88, in _run_code File "/home/swarming/.swarming/swarming_bot.zip/__main__.py", line 31, in THIS_FILE = os.path.abspath(zip_package.get_main_script_path()) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^ File "/home/swarming/.swarming/swarming_bot.zip/utils/zip_package.py", line 238, in get_main_script_path path = get_module_zip_archive(main) File "/home/swarming/.swarming/swarming_bot.zip/utils/zip_package.py", line 217, in get_module_zip_archive loader = pkgutil.get_loader(module) ^^^^^^^^^^^^^^^^^^ AttributeError: module 'pkgutil' has no attribute 'get_loader' 2026/06/28 18:16:33 command execution /usr/local/bin/python3 /home/swarming/.swarming/swarming_bot.zip start_bot: exit status 1

What did you expect to see?

pkgutil.get_loader was deprecated a while ago and apparently was removed in Python 3.14. Has LUCI already been updated but my builder machine is not getting the update, or is this an update needed in LUCI?

[n2vi]

@golang/release

[gabyhelp]

Related Issues

• x/build: LUCI support for plan9 #62025 (closed)
• x/build: failed to start OpenBSD-riscv64 LUCI builder #64797 (closed)

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[dmitshur]

As far as I can tell, the swarming bot code hasn't been updated to be compatible with Python 3.14 yet, and you're among the first to notice and report this. I see that pkgutil.get_loader call is still there on line 217 in the latest version of luci/client/utils/zip_package.py as of this posting. So this isn't due to the update mechanism not working.

From looking at the logs of a typical linux-amd64 builder, the python version being fetched there seems to be 3.11.9, way before pkgutil.get_loader was removed. There's a dimension for the python version, which makes it convenient to see what other LUCI bots are using: not a single bot running Python 3.14 (https://chromium-swarm.appspot.com/botlist?f=python%3A3.14), some running 3.13 (https://chromium-swarm.appspot.com/botlist?f=python%3A3.13), and many running older versions of Python 3.

The next steps here would be to file a bug in the LUCI issue tracker at https://issues.chromium.org/issues?q=status:open%20componentid:1456370, or perhaps rely on the existing https://issues.chromium.org/issues/40618684 tracking bug. Until the swarming bot is updated to support Python 3.14+, a workaround is to stay with 3.13.

[n2vi]

Filed https://issues.chromium.org/issues/536346612.