Import BytesIO from io

[effigies]

>>> import nibabel
[...]/nibabel/cifti2/parse_cifti2.py:24: FutureWarning: We no longer carry a copy of the 'six' package in nibabel; Please import the 'six' package directly
  from ..externals.six import BytesIO

This PR also updates a bunch of from six import BytesIO imports I found while making sure that was the only thing still importing from externals.six.

[matthew-brett]

Looks good - are you happy with just this change, or are there more to come?

Would you mind rebasing?

[effigies]

Yeah, I'll rebase before this goes in. I'm a little curious why that first one failed, so I want to run these tests. I'll ping you once I've stopped tinkering.

[codecov-io]

Codecov Report

Merging #519 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #519   +/-   ##
=======================================
  Coverage   94.14%   94.14%           
=======================================
  Files         175      175           
  Lines       23887    23887           
  Branches     2568     2568           
=======================================
  Hits        22489    22489           
  Misses        918      918           
  Partials      480      480

Impacted Files	Coverage Δ
nibabel/tests/test_image_load_save.py	96.33% <100%> (ø)	⬆️
nibabel/tests/test_arraywriters.py	96.2% <100%> (ø)	⬆️
nibabel/tests/test_files_interface.py	97.05% <100%> (ø)	⬆️
nibabel/tests/test_arrayproxy.py	100% <100%> (ø)	⬆️
nibabel/tests/test_fileholders.py	100% <100%> (ø)	⬆️
nibabel/freesurfer/tests/test_mghformat.py	100% <100%> (ø)	⬆️
nibabel/streamlines/tests/test_trk.py	100% <100%> (ø)	⬆️
nibabel/tests/test_wrapstruct.py	92.23% <100%> (+0.02%)	⬆️
nibabel/cifti2/parse_cifti2.py	82.96% <100%> (ø)	⬆️
nibabel/streamlines/tests/test_streamlines.py	95.36% <100%> (ø)	⬆️
... and 10 more

---

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[coveralls]

Coverage remained the same at 96.157% when pulling d0ea42e on effigies:remove_six into 6f58e02 on nipy:master.

[matthew-brett]

I did try this refactoring a while back, but ran into the same trouble and backed off.

The differences come from the fact thatfrom six import BytesIO, StringIO both result in StringIO.StringIO in Python 2.7. StringIO.StringIO accepts and returns not-unicode strings; as expected by the tests - that causes some of the errors. io.BytesIO can't be pickled, causing another error. I can't remember the explanation for the other errors, but I concluded that it wasn't worth refactoring round them. Maybe you'll come to a different conclusion though...

[effigies]

Yeah, not planning on refactoring, but I do want to see which ones are safe to switch. Latest commit looks to be building fine on Travis. At least now we're down to:

$ grep -rI IO nibabel | grep 'six import'
nibabel/externals/tests/test_six.py:        from six import BytesIO
nibabel/tests/test_analyze.py:from six import BytesIO, StringIO
nibabel/tests/test_batteryrunners.py:from six import StringIO
nibabel/tests/test_wrapstruct.py:from six import StringIO

If someone decides to tackle those last few imports, at least the scope will be clearer.

Squashing...

[coveralls]

Coverage remained the same at 96.157% when pulling d0bb37d on effigies:remove_six into 6f58e02 on nipy:master.

[effigies]

Rebased. I'll merge when (assuming) the tests pass, unless you'd rather do the honors?

[matthew-brett]

Go for it.

[coveralls]

Coverage remained the same at 96.157% when pulling c381801 on effigies:remove_six into 6f58e02 on nipy:master.