BUG: update cython to fix segfault accessing __kwdefaults__

[jakebailey]

• closes Inspection of some cython produced functions causes segfault #26127
• tests added / passed
• passes git diff upstream/master -u -- "*.py" | flake8 --diff
• whatsnew entry

This ups the cython minimum version to fix bugs as seen in #26127. I've added a test which goes through the members of _libs to check that they don't segfault when accessed. If you manually install 0.28.2 and run the test, you'll see it segfault.

I'm not sure how to place this change in the "whatsnow", so I'd be happy if I could get some advice there (and anywhere else I've gone wrong, of course).

[jakebailey]

Actually, I'm seeing mentions of cython version requirements in v0.23.0.rst and v0.24.0.rst, so maybe that's the place to put it.

[codecov]

Codecov Report

Merging #26140 into master will decrease coverage by 51.25%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           master   #26140       +/-   ##
===========================================
- Coverage   91.99%   40.73%   -51.26%     
===========================================
  Files         175      175               
  Lines       52382    52382               
===========================================
- Hits        48188    21338    -26850     
- Misses       4194    31044    +26850

Flag	Coverage Δ
#multiple	?
#single	40.73% <ø> (-0.14%)	⬇️

Impacted Files	Coverage Δ
pandas/io/formats/latex.py	0% <0%> (-100%)	⬇️
pandas/io/sas/sas_constants.py	0% <0%> (-100%)	⬇️
pandas/core/groupby/categorical.py	0% <0%> (-100%)	⬇️
pandas/tseries/plotting.py	0% <0%> (-100%)	⬇️
pandas/tseries/converter.py	0% <0%> (-100%)	⬇️
pandas/io/formats/html.py	0% <0%> (-99.37%)	⬇️
pandas/io/sas/sas7bdat.py	0% <0%> (-91.16%)	⬇️
pandas/io/sas/sas_xport.py	0% <0%> (-90.1%)	⬇️
pandas/core/tools/numeric.py	10.44% <0%> (-89.56%)	⬇️
pandas/io/s3.py	0% <0%> (-89.48%)	⬇️
... and 130 more

---

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[codecov]

Codecov Report

Merging #26140 into master will decrease coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #26140      +/-   ##
==========================================
- Coverage   91.99%   91.98%   -0.01%     
==========================================
  Files         175      175              
  Lines       52382    52382              
==========================================
- Hits        48188    48184       -4     
- Misses       4194     4198       +4

Flag	Coverage Δ
#multiple	90.54% <ø> (ø)	⬆️
#single	40.73% <ø> (-0.14%)	⬇️

Impacted Files	Coverage Δ
pandas/io/gbq.py	75% <0%> (-12.5%)	⬇️
pandas/core/frame.py	96.9% <0%> (-0.12%)	⬇️

---

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Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
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[jakebailey]

Interesting, the 3.5 machines can't install cython 0.29.7 even though it should be available.

[WillAyd]

Might be an issue of availability of 3.5 builds for conda. @TomAugspurger if you have any insights

[jreback]

i am -1 on this bump
this has only been out for a month

[TomAugspurger]

We can certainly ensure that the next set of wheels are built with new enough Cython. That would be in the pandas-release repo.

…

On Apr 19, 2019, at 10:01, Jeff Reback ***@***.***> wrote: @jreback requested changes on this pull request. i am -1 on this bump this has only been out for a month — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub, or mute the thread.

[WillAyd]

Closing as I don't think we have interest in this PR as is given how recent the Cython release is. Can reevaluate at a later date!