Failing unit tests on Windows

[mrakitin]

The following error was observed when running the full test suite for a conda-forge recipe (see conda-forge/staged-recipes#15389 (comment)):

(%PREFIX%) %SRC_DIR%>pytest -v --pyargs area_detector_handlers 
============================= test session starts =============================
platform win32 -- Python 3.9.6, pytest-6.2.4, py-1.10.0, pluggy-0.13.1 -- %PREFIX%\python.exe
cachedir: .pytest_cache
rootdir: %SRC_DIR%
collecting ... collected 13 items

tests/test_eiger.py::test_eiger[EigerHandler] PASSED                     [  7%]
tests/test_eiger.py::test_eiger2[EigerHandler] PASSED                    [ 15%]
tests/test_eiger.py::test_eiger2[EigerHandler] ERROR                     [ 15%]
tests/test_entrypoints.py::test_entrypoint_consisetncy PASSED            [ 23%]
tests/test_examples.py::test_context PASSED                              [ 30%]
tests/test_hdf5.py::test_hdf5[1-AreaDetectorHDF5Handler] PASSED          [ 38%]
tests/test_hdf5.py::test_hdf5_slicing_bound_exception[1-AreaDetectorHDF5Handler] PASSED [ 46%]
tests/test_hdf5.py::test_hdf5[5-AreaDetectorHDF5Handler] PASSED          [ 53%]
tests/test_hdf5.py::test_hdf5_slicing_bound_exception[5-AreaDetectorHDF5Handler] PASSED [ 61%]
tests/test_imm.py::test_imm[IMMHandler-B020_bluesky_demo_00001-00021.imm-21-frame_shape0] PASSED [ 69%]
tests/test_tiff.py::test_tiff[1-AreaDetectorTiffHandler] PASSED          [ 76%]
tests/test_tiff.py::test_tiff[5-AreaDetectorTiffHandler] PASSED          [ 84%]
tests/test_xs3.py::test_bulk[BulkXSPRESS] PASSED                         [ 92%]
tests/test_xs3.py::test_pre_pixel[Xspress3HDF5Handler] PASSED            [100%]

=================================== ERRORS ====================================
_______________ ERROR at teardown of test_eiger2[EigerHandler] ________________

    def finalize():
        os.remove(out_name)
>       os.remove("sample_data_000001.h5")
E       PermissionError: [WinError 32] The process cannot access the file because it is being used by another process: 'sample_data_000001.h5'

..\_test_env\lib\site-packages\area_detector_handlers\tests\conftest.py:82: PermissionError
============================== warnings summary ===============================
..\_test_env\lib\site-packages\pyreadline\py3k_compat.py:8
  %PREFIX%\lib\site-packages\pyreadline\py3k_compat.py:8: DeprecationWarning: Using or importing the ABCs from 'collections' instead of from 'collections.abc' is deprecated since Python 3.3, and in 3.10 it will stop working
    return isinstance(x, collections.Callable)

-- Docs: https://docs.pytest.org/en/stable/warnings.html
=========================== short test summary info ===========================
ERROR tests/test_eiger.py::test_eiger2[EigerHandler] - PermissionError: [WinE...
=================== 13 passed, 1 warning, 1 error in 2.88s ====================