Fix CI

[martinRenou]

No description provided.

[rmorshea]

@martinRenou is this related? #497

[martinRenou]

I'm not quite sure it's related to Sentinel not being exported. I'm trying to fix the

/home/travis/virtualenv/python3.6.3/lib/python3.6/site-packages/pytest_warnings/__init__.py:44: UserWarning: pytest-warnings plugin was introduced in core pytest on 3.1, please uninstall pytest-warnings
  warnings.warn('pytest-warnings plugin was introduced in core pytest on 3.1, please '
Traceback (most recent call last):
  File "/home/travis/virtualenv/python3.6.3/lib/python3.6/site-packages/pluggy/__init__.py", line 397, in load_setuptools_entrypoints
    plugin = ep.load()
  File "/home/travis/virtualenv/python3.6.3/lib/python3.6/site-packages/pkg_resources/__init__.py", line 2404, in load
    self.require(*args, **kwargs)
  File "/home/travis/virtualenv/python3.6.3/lib/python3.6/site-packages/pkg_resources/__init__.py", line 2427, in require
    items = working_set.resolve(reqs, env, installer, extras=self.extras)
  File "/home/travis/virtualenv/python3.6.3/lib/python3.6/site-packages/pkg_resources/__init__.py", line 875, in resolve
    raise VersionConflict(dist, req).with_context(dependent_req)
pkg_resources.VersionConflict: (pytest 3.3.0 (/home/travis/virtualenv/python3.6.3/lib/python3.6/site-packages), Requirement.parse('pytest>=3.6'))

That you can see on those builds: https://travis-ci.org/ipython/traitlets/jobs/513025651

[rmorshea]

Hmm, this looks like pytest 3.3 has already been installed inside the virtualenv, but something is requiring >=3.6

[martinRenou]

Yeah, there is also this warning: pytest-warnings plugin was introduced in core pytest on 3.1, please uninstall pytest-warnings

[rmorshea]

I wonder whether this would be fixed if you set pytest==3.3 here since it seems like its during the installation of extras for traitlets that we're encountering this error.

[minrk]

This now gets the tests passing, except for what are actual failing traittypes tests due to a breaking change in traitlets, in our handling of Undefined. This is open on traittypes as jupyter-widgets/traittypes#33 since it seems like what they are doing doesn't make a lot of sense, and I'm a little surprised it works in stable traitlets.

[minrk]

Thanks for the PR!

[martinRenou]

Sure! I also noticed the tests are using deprecated stuff:
DeprecationWarning: on_trait_change is deprecated in traitlets 4.1: use observe instead

[minrk]

Yeah, the tests verify that deprecated APIs still work, we shouldn't stop testing them. We could suppress the warnings, though.