test_serialize: Silence pynwb warning

pynwb 3.1.2 does currently always output a warning about a missing .nwb
ending in path even if path was not passed at all and is None.

This will be fixed in [1], ignore the warning until we require that
version.

We also drop the path argument to NWBHDF5IO as that is not needed.

[1]: NeurodataWithoutBorders/pynwb#2130

Author: t-b

tests/attach_metadata/test_nwb2_sink.py

@@ -80,6 +80,7 @@ def test_get_subject(nwbfile, set_none):
 
 
 @pytest.mark.filterwarnings("ignore:.*Value with data type int64 is being converted to data type uint64.*")
+@pytest.mark.filterwarnings("ignore:.*It is recommended that NWB files using the HDF5 backend use the '.nwb' extension.")
 def test_serialize(tmpdir_factory, nwbfile):
     out_path = os.path.join(
         str(tmpdir_factory.mktemp("test_serialize")),
@@ -90,7 +91,6 @@ def test_serialize(tmpdir_factory, nwbfile):
     sink._data = io.BytesIO()
     sink._h5_file = h5py.File(sink._data, "w")
     sink._nwb_io = pynwb.NWBHDF5IO(
-        path=sink._h5_file.filename,
         mode="w",
         file=sink._h5_file
     )