netcdf4/h5netcdf cross engine test broken on Python 2

[QuLogic]

This is not really a bugfix or enhancement. In fact, it's just a bug report right now. I'm having trouble running tests on Python 2 with both netcdf4 and h5netcdf installed due to the cross engine test (
H5NetCDFDataTest.test_cross_engine_read_write_netcdf4).

I noticed that the requirements list netcdf4 twice; I assume this was a typo and the second one should be h5netcdf. By switching the duplicate out, I'm hoping to trigger the problem on CI as a way to report this bug.

• closes #xxxx
• tests added / passed
• passes git diff upstream/master | flake8 --diff
• whatsnew entry

[QuLogic]

Fortunately, this does fail in the same way as it does for me locally. Since Python 3 works, I think this might be a bytes/str thing, but the error is a bit opaque to me.

[fmaussion]

The test that fails is called test_cross_engine_read_write_netcdf4, so it looks like it's more of a testing bug that an issue in xarray (the tests shouldn't run when netcdf4 isn't installed).

[QuLogic]

Both netcdf4 and h5netcdf are installed now; that's the point.

[QuLogic]

h5netcdf/h5netcdf#16 appears to be the upstream issue, but oddly, it seems to be reported against Python 3 when here it fails with Python 2.

[QuLogic]

Oh, just realized there's a skip on Python 3, which links to #535. Apparently, this test is now broken on both Python versions.

[shoyer]

Thanks for figuring this out -- I fixed our test suite in #1336. I'm looking forward to the next netCDF release, at which point h5netcdf will stop having this issue!