Analyse following RPM build log snippet. Describe contents accurately, without speculation or suggestions for resolution.            
Your analysis must be as concise as possible, while keeping relevant information intact.
Snippet: 
ERROR    ocrmypdf._pipelines._common:_common.py:296 An exception occurred while executing the pipeline
Traceback (most recent call last):
  File "/builddir/build/BUILD/ocrmypdf-16.7.0-build/BUILDROOT/usr/lib/python3.14/site-packages/ocrmypdf/_pipelines/_common.py", line 261, in cli_exception_handler
    return fn(options, plugin_manager)
  File "/builddir/build/BUILD/ocrmypdf-16.7.0-build/BUILDROOT/usr/lib/python3.14/site-packages/ocrmypdf/_pipelines/ocr.py", line 181, in _run_pipeline
    optimize_messages = exec_concurrent(context, executor)
  File "/builddir/build/BUILD/ocrmypdf-16.7.0-build/BUILDROOT/usr/lib/python3.14/site-packages/ocrmypdf/_pipelines/ocr.py", line 145, in exec_concurrent
    pdf, messages = postprocess(pdf, context, executor)
                    ~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^
  File "/builddir/build/BUILD/ocrmypdf-16.7.0-build/BUILDROOT/usr/lib/python3.14/site-packages/ocrmypdf/_pipelines/_common.py", line 460, in postprocess
    return optimize_pdf(pdf_out, context, executor)
  File "/builddir/build/BUILD/ocrmypdf-16.7.0-build/BUILDROOT/usr/lib/python3.14/site-packages/ocrmypdf/_pipeline.py", line 984, in optimize_pdf
    output_pdf, messages = context.plugin_manager.hook.optimize_pdf(
                           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
        input_pdf=input_file,
        ^^^^^^^^^^^^^^^^^^^^^
    ...<3 lines>...
        linearize=should_linearize(input_file, context),
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    )
    ^
  File "/usr/lib/python3.14/site-packages/pluggy/_hooks.py", line 513, in __call__
    return self._hookexec(self.name, self._hookimpls.copy(), kwargs, firstresult)
           ~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.14/site-packages/pluggy/_manager.py", line 120, in _hookexec
    return self._inner_hookexec(hook_name, methods, kwargs, firstresult)
           ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.14/site-packages/pluggy/_callers.py", line 139, in _multicall
    raise exception.with_traceback(exception.__traceback__)
  File "/usr/lib/python3.14/site-packages/pluggy/_callers.py", line 103, in _multicall
    res = hook_impl.function(*args)
  File "/builddir/build/BUILD/ocrmypdf-16.7.0-build/BUILDROOT/usr/lib/python3.14/site-packages/ocrmypdf/builtin_plugins/optimize.py", line 145, in optimize_pdf
    result_path = optimize(input_pdf, output_pdf, context, save_settings, executor)
  File "/builddir/build/BUILD/ocrmypdf-16.7.0-build/BUILDROOT/usr/lib/python3.14/site-packages/ocrmypdf/optimize.py", line 705, in optimize
    deflate_jpegs(pdf, root, options, executor)
    ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/builddir/build/BUILD/ocrmypdf-16.7.0-build/BUILDROOT/usr/lib/python3.14/site-packages/ocrmypdf/optimize.py", line 575, in deflate_jpegs
    executor(
    ~~~~~~~~^
        use_threads=True,  # We're sharing the pdf directly, must use threads
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    ...<9 lines>...
        task_finished=finish,
        ^^^^^^^^^^^^^^^^^^^^^
    )
    ^
  File "/builddir/build/BUILD/ocrmypdf-16.7.0-build/BUILDROOT/usr/lib/python3.14/site-packages/ocrmypdf/_concurrent.py", line 78, in __call__
    self._execute(
    ~~~~~~~~~~~~~^
        use_threads=use_threads,
        ^^^^^^^^^^^^^^^^^^^^^^^^
    ...<5 lines>...
        task_finished=task_finished,
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    )
    ^
  File "/builddir/build/BUILD/ocrmypdf-16.7.0-build/BUILDROOT/usr/lib/python3.14/site-packages/ocrmypdf/extra_plugins/semfree.py", line 157, in _execute
    process.start()
    ~~~~~~~~~~~~~^^
  File "/usr/lib64/python3.14/multiprocessing/process.py", line 121, in start
    self._popen = self._Popen(self)
                  ~~~~~~~~~~~^^^^^^
  File "/usr/lib64/python3.14/multiprocessing/context.py", line 224, in _Popen
    return _default_context.get_context().Process._Popen(process_obj)
           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
  File "/usr/lib64/python3.14/multiprocessing/context.py", line 300, in _Popen
    return Popen(process_obj)
  File "/usr/lib64/python3.14/multiprocessing/popen_forkserver.py", line 35, in __init__
    super().__init__(process_obj)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
  File "/usr/lib64/python3.14/multiprocessing/popen_fork.py", line 20, in __init__
    self._launch(process_obj)
    ~~~~~~~~~~~~^^^^^^^^^^^^^
  File "/usr/lib64/python3.14/multiprocessing/popen_forkserver.py", line 47, in _launch
    reduction.dump(process_obj, buf)
    ~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^
  File "/usr/lib64/python3.14/multiprocessing/reduction.py", line 60, in dump
    ForkingPickler(file, protocol).dump(obj)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^
TypeError: cannot pickle 'pikepdf._core.Pdf' object
when serializing tuple item 0
when serializing list item 0
when serializing tuple item 4
when serializing dict item '_args'
when serializing multiprocessing.context.Process state
when serializing multiprocessing.context.Process object

Answer: This shows an extended log of the failed test. The error originates in multiprocessing library with Python 3.14. The test code starts a new process with a context called "forkserver" and it is unsuccessful. This failure is displayed as TypeError: cannot pickle 'pikepdf._core.Pdf' object, but the actual issue comes from from multiprocessing module.