sudo: false
cache:
  directories:
    - $HOME/.cache/pip
language: python
matrix:
  include:
    - python: 2.7
      env: TOXENV=py27,py27-flake8
    - python: 3.4
      env: TOXENV=py34
    - python: 3.5
      env: TOXENV=py35
    - python: 3.6
      env: TOXENV=py36,py36-flake8
    - python: pypy
      env: TOXENV=pypy
    - python: pypy3
      env: TOXENV=pypy3

services:
  - memcached

install:
  - travis_retry pip install tox

script:
  - travis_retry tox -- -m unit,integration

sudo: false
cache: pip
language: python
matrix:
  include:
    - python: 2.7
      env: TOXENV=py27,py27-flake8
    - python: 3.4
      env: TOXENV=py34
    - python: 3.5
      env: TOXENV=py35
    - python: 3.6
      env: TOXENV=py36,py36-flake8
    - python: pypy
      env: TOXENV=pypy
    - python: pypy3
      env: TOXENV=pypy3

services:
  - memcached

install:
  - travis_retry pip install tox

script:
  - travis_retry tox -- -m unit,integration

Use simpler Travis pip caching syntax
Use simpler Travis pip caching syntax

The previous directory-based caching directive worked fine, but using
the generic `pip` syntax is simpler and more future-proof.
