PR #276 Travis CI checks failed due to an issue with the slycot builds. See Travis CI build 400.01, line 954. I did a quick check and it looks like there is a problem with skbuild:

Traceback (most recent call last):
  File "setup.py", line 8, in <module>
    from skbuild import setup
ModuleNotFoundError: No module named 'skbuild'
0.03s$ if [ $SLYCOT != "" ]; then python -c "import slycot"; fi

Not sure if this is something transient or something that has changed in scikit (and not quite sure why slycot needs scikit).