CI: Travis tests timing out
E.g. https://travis-ci.org/pandas-dev/pandas/jobs/417983438

```
........................................................................ [ 95%]
.......................
No output has been received in the last 10m0s, this potentially indicates a stalled build or something wrong with the build itself.
Check the details on how to adjust your build configuration on: https://docs.travis-ci.com/user/common-build-problems/#Build-times-out-because-no-output-was-received
The build has been terminated
```