Resolve warnings in CI

Each of the CI runs have hundreds of warnings. Here are the ones presented in the pytest warnings summary, so probably some of the most important ones. These warnings should be resolved before they turn into errors.

Integration tests

• tests/integration/api_test.py::test_api_markdown_editor[flask-chromium]
    /opt/hostedtoolcache/Python/3.8.18/x64/lib/python3.8/site-packages/traitlets/__init__.py:26: DeprecationWarning: 
                Sentinel is not a public part of the traitlets API.
                It was published by mistake, and may be removed in the future.
                
      warn(
  

• tests/integration/api_test.py::test_api_markdown_editor[flask-chromium]
    /opt/hostedtoolcache/Python/3.8.18/x64/lib/python3.8/site-packages/traittypes/traittypes.py:188: DeprecationWarning: metadata {'dtype': None} was set from the constructor. With traitlets 4.1, metadata should be set using the .tag() method, e.g., Int().tag(key1='value1', key2='value2')
      super(DataFrame, self).__init__(
  

• tests/integration/file_download_test.py: 20 warnings
    /opt/hostedtoolcache/Python/3.8.18/x64/lib/python3.8/site-packages/solara/hooks/use_thread.py:128: DeprecationWarning: use_side_effect is deprecated, please use use_effect
      solara.use_side_effect(run, dependencies + [counter])
  

• tests/integration/server_test.py: 20 warnings
    /home/runner/work/solara/solara/tests/integration/server_test.py:71: DeprecationWarning:
    
    use_side_effect is deprecated, please use use_effect
  

• tests/integration/file_download_test.py: 20 warnings
    /opt/hostedtoolcache/Python/3.8.18/x64/lib/python3.8/site-packages/solara/hooks/use_thread.py:128: DeprecationWarning:
    
    use_side_effect is deprecated, please use use_effectl
  

Unit tests

All Python versions

• ../../../../../opt/hostedtoolcache/Python/3.6.15/x64/lib/python3.6/site-packages/bqplot/marks.py:167
  
    /opt/hostedtoolcache/Python/3.6.15/x64/lib/python3.6/site-packages/bqplot/marks.py:167: DeprecationWarning:
  
  
    metadata {'value_trait': <traitlets.traitlets.Instance object at 0x7fcb84[61](https://github.com/widgetti/solara/actions/runs/6698250420/job/18199885568#step:6:62)0c18>} was set from the constructor. With traitlets 4.1, metadata should be set using the .tag() method, e.g., Int().tag(key1='value1', key2='value2')
  

• ../../../../../opt/hostedtoolcache/Python/3.6.15/x[64](https://github.com/widgetti/solara/actions/runs/6698250420/job/18199885568#step:6:65)/lib/python3.6/site-packages/bqplot/plotting_widgets.py:30
    /opt/hostedtoolcache/Python/3.6.15/x64/lib/python3.6/site-packages/bqplot/plotting_widgets.py:30: DeprecationWarning:
  
  
    metadata {'dtype': None} was set from the constructor. With traitlets 4.1, metadata should be set using the .tag() method, e.g., Int().tag(key1='value1', key2='value2')
  

• tests/unit/cache_test.py::test_cache_redis
    /opt/hostedtoolcache/Python/3.6.15/x64/lib/python3.6/site-packages/redis/utils.py:13: CryptographyDeprecationWarning:
  
  
    Python 3.6 is no longer supported by the Python core team. Therefore, support for it is deprecated in cryptography. The next release of cryptography will remove support for Python 3.6.
  

•   /opt/hostedtoolcache/Python/3.6.15/x64/lib/python3.6/site-packages/solara/hooks/use_thread.py:128: DeprecationWarning:
  
  
    use_side_effect is deprecated, please use use_effect
  

• tests/unit/dataframe_test.py::test_table
    /opt/hostedtoolcache/Python/3.6.15/x64/lib/python3.6/site-packages/solara/components/dataframe.py:[79](https://github.com/widgetti/solara/actions/runs/6698250420/job/18199885568#step:6:80): DeprecationWarning:
  
  
    use_side_effect is deprecated, please use use_effect
  

• tests/unit/hooks_test.py::test_hook_iterator
    /opt/hostedtoolcache/Python/3.6.15/x64/lib/python3.6/contextlib.py:99: DeprecationWarning:
  
  
    generator 'cancel_guard' raised StopIteration
  

• tests/unit/kernel_test.py::test_session_datetime
    /opt/hostedtoolcache/Python/3.6.15/x64/lib/python3.6/json/encoder.py:199: DeprecationWarning:
  
  
    Interpreting naive datetime as local 2023-10-30 20:22:51.449402. Please add timezone info to timestamps.
  

Python 3.9+ specific

Warnings that appear in Python 3.9 CI run, but not in the 3.6 one

• tests/unit/pivottable_test.py: 81 warnings
    /opt/hostedtoolcache/Python/3.9.18/x64/lib/python3.9/ast.py:407: DeprecationWarning:
    
    visit_NameConstant is deprecated; add visit_Constant
  

• tests/unit/dataframe_test.py: 4 warnings
    /opt/hostedtoolcache/Python/3.9.18/x64/lib/python3.9/site-packages/vaex/cpu.py:527: DeprecationWarning:
    
    np.find_common_type is deprecated.  Please use `np.result_type` or `np.promote_types`.
    See https://numpy.org/devdocs/release/1.25.0-notes.html and the docs for more information.  (Deprecated NumPy 1.25)
  

• tests/unit/pivottable_test.py: 7 warnings
    /opt/hostedtoolcache/Python/3.9.18/x64/lib/python3.9/ast.py:407: DeprecationWarning:
    
    visit_Num is deprecated; add visit_Constant
  

• tests/unit/pivottable_test.py: 59 warnings
    /opt/hostedtoolcache/Python/3.9.18/x64/lib/python3.9/ast.py:407: DeprecationWarning:
    
    visit_Str is deprecated; add visit_Constant
  

• tests/unit/toestand_test.py::test_thread_local
    /opt/hostedtoolcache/Python/3.9.18/x64/lib/python3.9/site-packages/_pytest/threadexception.py:73: PytestUnhandledThreadExceptionWarning:
    
    Exception in thread Thread-102
    
    Traceback (most recent call last):
      File "/opt/hostedtoolcache/Python/3.9.18/x64/lib/python3.9/threading.py", line 980, in _bootstrap_inner
        self.run()
      File "/opt/hostedtoolcache/Python/3.9.18/x64/lib/python3.9/site-packages/solara/server/patch.py", line 257, in Thread_debug_run
        Thread__run(self)
      File "/opt/hostedtoolcache/Python/3.9.18/x64/lib/python3.9/threading.py", line 917, in run
        self._target(*self._args, **self._kwargs)
      File "/home/runner/work/solara/solara/tests/unit/toestand_test.py", line 777, in test3
        assert solara.lab.thread_local.reactive_used is None
      File "/opt/hostedtoolcache/Python/3.9.18/x64/lib/python3.9/site-packages/solara/lab/__init__.py", line 30, in __getattr__
        raise AttributeError(f"module '{__name__}' has no attribute '{name}'")
    AttributeError: module 'solara.lab' has no attribute 'thread_local'
  

ipywidgets 8.x specific

Warnings that appear in ipywidgets 8.x CI run, but not in the 7.7. one

• ../../../../../opt/hostedtoolcache/Python/3.9.18/x64/lib/python3.9/site-packages/vaex/dataset_mmap.py:101: 130 warnings
    /opt/hostedtoolcache/Python/3.9.18/x64/lib/python3.9/site-packages/vaex/dataset_mmap.py:101: DeprecationWarning: `product` is deprecated as of NumPy 1.25.0, and will be removed in NumPy 2.0. Please use `prod` instead.
      return self._do_map(path, offset, shape, dtype)
  

Start by rerunning the integration and unittest CI workflows linked in the issue, then group the warnings by the listed tests and source paths. Inspect the affected Solara tests and package warnings to determine which are actionable; done means the listed warnings are resolved or otherwise no longer appear in CI.