CI: travis-36-cov failing
I'm seeing

```
from ._openmp_helpers import _openmp_parallelism_enabled
ImportError: dlopen: cannot load any more object with static TLS
```

in e.g. https://travis-ci.org/pandas-dev/pandas/jobs/626304911#L648

Still debugging. scikit-learn 0.22 was just released to defaults. Some of our deps look fishy there (mixing defaults and conda-forge a bunch).