CI: Install pytest>=3.4 in Travis

[effigies]

Summary

pytest-xdist 1.22.4 bumped their requirement to pytest >=3.4 (ours is >=3.0). It's unclear why this is failing to resolve. Creating this issue to see if there's a conflict.

See Travis errors in #2658.

Possibly related: #2649

Acknowledgment

• (Mandatory) I acknowledge that this contribution will be available under the Apache 2 license.

[djarecka]

it looks like they just had a new release. If you have problem, we can temporary change to 1.22.3, it was working

[effigies]

That might be a better solution. Hopefully it's just a temporary resolution error and we don't actually have any conflicts that prevent us from using >=3.4, since the current pytest series is 3.6.x.

[codecov-io]

Codecov Report

Merging #2659 into master will decrease coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #2659      +/-   ##
==========================================
- Coverage   67.62%   67.61%   -0.01%     
==========================================
  Files         340      340              
  Lines       43054    43054              
  Branches     5329     5329              
==========================================
- Hits        29115    29113       -2     
- Misses      13237    13240       +3     
+ Partials      702      701       -1

Flag	Coverage Δ
#smoketests	50.51% <100%> (ø)	⬆️
#unittests	65.08% <100%> (-0.01%)	⬇️

Impacted Files	Coverage Δ
nipype/info.py	94.02% <100%> (ø)	⬆️
nipype/interfaces/dipy/setup.py	0% <0%> (-25%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update aeb0874...0884e27. Read the comment docs.

[djarecka]

@effigies - I'll merge it to #2637, so the tests can run

[djarecka]

or can we just merge to master? looks like everyone is happy with pytest>3.4

[effigies]

Yeah, updating pip wasn't sufficient to get pip to correctly resolve the dependency. The only alternative I see is to add a pip install --upgrade pytest>=3.4 to Travis.

@satra @oesteban Any thoughts on the best way to proceed? 3.4 is from this year, so this is a fairly strong constraint for people who don't need the latest pytest-xdist.

[djarecka]

@effigies - not sure why this is a problem. If they already have old pytest-xdist the older pytest will work. If they somehow got pytest-xdist that was released today morning, they should be ok with getting pytest from Jan.

[effigies]

Sure. But now we're requiring pytest 3.4. In general, it's good to be as flexible as possible to avoid putting users in a place where they have conflicting requirements. For instance, suppose somebody has a package that requires pytest<=3.3, and they have some pytest-xdist that is compatible with pytest==3.3. Now they want to install nipype==1.1.1, and suddenly they have an unresolvable dependency conflict. We don't actually need pytest 3.4, but the latest version of one of our dependencies causes tests to break on Travis, so we update it... It's not ideal.

[djarecka]

@effigies - so one option would be to remove xdist, i.e. pytest -n from nipype.test() and keep it only for "test" installation, for people who want to test it regularly

[effigies]

Eh. I decided to go the Travis hack route. It really is just a quirk of Travis' default python environment and a pip bug. Keeping a reasonable set of dependencies shouldn't affect typical users. If I'm wrong, and we need to update the dependency in the future, we can.

[djarecka]

@effigies - but the standard pip installation of nipype will not lead to the error for nipype.test()?

[effigies]

The case in which it does is if you have pytest>=3.0,<3.4 already installed, but not pytest-xdist.

Sure there might be some setups like that, and we can walk people through some solution that fits their needs. Likely pip install --upgrade pytest is sufficient, but at least we won't be imposing an unresolvable dependency conflict.

[djarecka]

ok, we can wait and see if anyone complains