BUG: Travis building on container-based infrastructure
- [ ] closes #10598
- [x] passes `git diff upstream/master | flake8 --diff`
- [ ] whatsnew entry

Travis is not always detecting sudo use and is running forks using container-based infrastructure. `JOB_NAME=27_slow_nnet_LOCALE` fails when using containers because of setlocale. This PR adds `sudo: required` to make sure travis does not use containers while sudo is needed in the travis set up scripts. 

Example: 
- https://travis-ci.org/nparley/pandas/jobs/124695152 (container)
- https://travis-ci.org/nparley/pandas/jobs/124778492 (non container)
