criu fails to build with Python 3.14.0b1.
The error comes from protobuf which doesn't work with Python 3.14 - it's reported in https://bugzilla.redhat.com/show_bug.cgi?id=2343969 but as we approach mass rebuild, I decided to raise this also with some of the dependent packages to increase visibility of the issue.

Processing ./lib
  Preparing metadata (pyproject.toml): started
  Preparing metadata (pyproject.toml): finished with status 'error'
  error: subprocess-exited-with-error
  
  × Preparing metadata (pyproject.toml) did not run successfully.
  │ exit code: 1
  ╰─> [80 lines of output]
      Traceback (most recent call last):
        File "/usr/lib/python3.14/site-packages/setuptools/config/expand.py", line 71, in __getattr__
          return next(
              ast.literal_eval(value)
              for target, value in self._find_assignments()
              if isinstance(target, ast.Name) and target.id == attr
          )
      StopIteration
      
      The above exception was the direct cause of the following exception:
      
      Traceback (most recent call last):
        File "/usr/lib/python3.14/site-packages/setuptools/config/expand.py", line 185, in read_attr
          value = getattr(StaticModule(module_name, spec), attr_name)
        File "/usr/lib/python3.14/site-packages/setuptools/config/expand.py", line 77, in __getattr__
          raise AttributeError(f"{self.name} has no attribute {attr}") from e
      AttributeError: pycriu has no attribute __version__
      
      During handling of the above exception, another exception occurred:
      
      Traceback (most recent call last):
        File "/usr/lib/python3.14/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 389, in <module>
          main()
          ~~~~^^
        File "/usr/lib/python3.14/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 373, in main
          json_out["return_val"] = hook(**hook_input["kwargs"])
                                   ~~~~^^^^^^^^^^^^^^^^^^^^^^^^
        File "/usr/lib/python3.14/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 175, in prepare_metadata_for_build_wheel
          return hook(metadata_directory, config_settings)
        File "/usr/lib/python3.14/site-packages/setuptools/build_meta.py", line 377, in prepare_metadata_for_build_wheel
          self.run_setup()
          ~~~~~~~~~~~~~~^^
        File "/usr/lib/python3.14/site-packages/setuptools/build_meta.py", line 320, in run_setup
          exec(code, locals())
          ~~~~^^^^^^^^^^^^^^^^
        File "<string>", line 6, in <module>
        File "/usr/lib/python3.14/site-packages/setuptools/__init__.py", line 117, in setup
          return distutils.core.setup(**attrs)
                 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^
        File "/usr/lib/python3.14/site-packages/setuptools/_distutils/core.py", line 160, in setup
          dist.parse_config_files()
          ~~~~~~~~~~~~~~~~~~~~~~~^^
        File "/usr/lib/python3.14/site-packages/setuptools/dist.py", line 752, in parse_config_files
          setupcfg.parse_configuration(
          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
              self, self.command_options, ignore_option_errors=ignore_option_errors
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
          )
          ^
        File "/usr/lib/python3.14/site-packages/setuptools/config/setupcfg.py", line 188, in parse_configuration
          meta.parse()
          ~~~~~~~~~~^^
        File "/usr/lib/python3.14/site-packages/setuptools/config/setupcfg.py", line 502, in parse
          section_parser_method(section_options)
          ~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
        File "/usr/lib/python3.14/site-packages/setuptools/config/setupcfg.py", line 477, in parse_section
          self[name] = value
          ~~~~^^^^^^
        File "/usr/lib/python3.14/site-packages/setuptools/config/setupcfg.py", line 294, in __setitem__
          parsed = self.parsers.get(option_name, lambda x: x)(value)
        File "/usr/lib/python3.14/site-packages/setuptools/config/setupcfg.py", line 600, in _parse_version
          return expand.version(self._parse_attr(value, self.package_dir, self.root_dir))
                                ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "/usr/lib/python3.14/site-packages/setuptools/config/setupcfg.py", line 419, in _parse_attr
          return expand.read_attr(attr_desc, package_dir, root_dir)
                 ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "/usr/lib/python3.14/site-packages/setuptools/config/expand.py", line 190, in read_attr
          module = _load_spec(spec, module_name)
        File "/usr/lib/python3.14/site-packages/setuptools/config/expand.py", line 211, in _load_spec
          spec.loader.exec_module(module)
          ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^
        File "<frozen importlib._bootstrap_external>", line 762, in exec_module
        File "<frozen importlib._bootstrap>", line 491, in _call_with_frames_removed
        File "/builddir/build/BUILD/criu-4.1-build/criu-4.1/lib/pycriu/__init__.py", line 1, in <module>
          from . import rpc_pb2 as rpc
        File "/builddir/build/BUILD/criu-4.1-build/criu-4.1/lib/pycriu/rpc_pb2.py", line 6, in <module>
          from google.protobuf import descriptor as _descriptor
        File "/usr/lib64/python3.14/site-packages/google/protobuf/descriptor.py", line 47, in <module>
          from google.protobuf.pyext import _message
      TypeError: Metaclasses with custom tp_new are not supported.
      [end of output]

https://docs.python.org/3.14/whatsnew/3.14.html

For the build logs, see:
https://copr-be.cloud.fedoraproject.org/results/@python/python3.14-b1/fedora-rawhide-x86_64/09026572-criu/

For all our attempts to build criu with Python 3.14, see:
https://copr.fedorainfracloud.org/coprs/g/python/python3.14-b1/package/criu/

Testing and mass rebuild of packages is happening in copr.
You can follow these instructions to test locally in mock if your package builds with Python 3.14:
https://copr.fedorainfracloud.org/coprs/g/python/python3.14-b1/

Let us know here if you have any questions.

Python 3.14 is planned to be included in Fedora 43.
To make that update smoother, we're building Fedora packages with all pre-releases of Python 3.14.
A build failure prevents us from testing all dependent packages (transitive [Build]Requires),
so if this package is required a lot, it's important for us to get it fixed soon.

We'd appreciate help from the people who know this package best,
but if you don't want to work on this now, let us know so we can try to work around it on our side.