language: python
python:
  - "2.7"
  - "3.4"
install:
  - pip install -r requirements.txt --use-mirrors
script:
  - nosetests dshelpers.py

language: python
python:
  - "2.7"
  - "3.4"
install:
  - pip install -r requirements.txt
script:
  - nosetests dshelpers.py

Remove --use-mirrors from pip command
Remove --use-mirrors from pip command

In .travis.yml: this isn't supported any more and cause build to fail.