tst: add py38 dev build

[mgxd]

builds off #81, adding a python 3.8 developmental build

[codecov]

Codecov Report

Merging #84 into master will increase coverage by 0.27%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master      #84      +/-   ##
==========================================
+ Coverage   86.14%   86.41%   +0.27%     
==========================================
  Files          12       12              
  Lines        2114     2157      +43     
  Branches      538      538              
==========================================
+ Hits         1821     1864      +43     
  Misses        205      205              
  Partials       88       88

Flag	Coverage Δ
#unittests	86.41% <ø> (+0.27%)	⬆️

Impacted Files	Coverage Δ
pydra/engine/state.py	94.82% <0%> (+0.09%)	⬆️
pydra/utils/messenger.py	92.85% <0%> (+0.1%)	⬆️
pydra/engine/graph.py	97.93% <0%> (+0.12%)	⬆️
pydra/engine/specs.py	96.72% <0%> (+0.16%)	⬆️
pydra/engine/helpers.py	83.63% <0%> (+0.3%)	⬆️
pydra/utils/profiler.py	39.55% <0%> (+0.45%)	⬆️
pydra/engine/core.py	87.46% <0%> (+0.52%)	⬆️
pydra/engine/task.py	81.94% <0%> (+0.78%)	⬆️

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[effigies]

Might be good also to do a pip install --pre to catch errors early.

[effigies]

Looks like you'll need to change L42:

-  - travis_retry python -m pip install --upgrade $INSTALL_DEPENDS
+  - PYTHONWARNINGS="" travis_retry python -m pip install --upgrade $INSTALL_DEPENDS

Alternately, use a different environment variable, like WARN="error" and change L87:

-        py.test -vs -n auto --cov pydra --cov-config .coveragerc --cov-report xml:cov.xml --doctest-modules pydra
+        PYTHONWARNINGS="$WARN" py.test -vs -n auto --cov pydra --cov-config .coveragerc --cov-report xml:cov.xml --doctest-modules pydra

The latter might be a little safer. On the whole, I'm more interested in warnings during execution than installation.

[mgxd]

@effigies increasing warning strictness is making the test a little too rigid, I'm inclined to revert the warnings level to default and just leave the --pre check.

[effigies]

Sure, that's fine for now. I'll open an issue about checking for warnings. Maybe pytest has a way of targeting warnings caused by our code better.