try fixing travis

.travis.yml

@@ -1,8 +1,7 @@
 language: python
 cache:
   yarn: true
-  directories:
-    - $HOME/.cache/pip
+  pip: true
 matrix:
   include:
   - env: 3
@@ -20,7 +19,6 @@ matrix:
   - env: GROUP=cli
   - env: GROUP=docs
 env:
-  global:
   - GH_REF: github.com/jupyterlab/jupyterlab.git
   - secure: MWpTI6cj3/Bnmtrr0Oqlp2JeWqDneB9aEjlQDaRxLOkqVbxhqDcYW9qAgZZP+sq29vT5oVMWzyCirteKxJfG2vy3HQE1XNLhz82Sf/7sE6DQ51gohl0CcOeA/uA8hCXEw97hneFWsZgHKqSoch7nVDsE3qfYgO+930jHlnxYApJGP9hZFv2Q2NVa6+99kipEYS4BY/yBDYKy6/t4kXcnBrUlNaPtdjnXcrY9esLZ7EQtkaG5VqcQVIBaLJKGF5Q7Aufj5nCFaZ6hZDF1Bi/AbmIbVWFyiT+22i8DZK6YwenECckyzoWkl+bEhYepWsgBKh/BDgPBAmPWKHgU5V4apDaGqZBhF7FP6H02AdZYYuCwl47jyakqvWLZW7oDmorL+HsWG5HQ3m0tMT2ywdbwNOiD39tiPPXjsvROh5ys9vL6NzQvxILCeEOnzcZrFuxi2LGEZfnlqRIjkh1llUAvNc3mOycRLWDOwVQa2+U59qDRXCSY2RD+MOfcdFUGengVujTMaAPMBUa3E33/ZIOOKJtR5TIajYZvd9B2uDlz02QfvTK+hrTaNYJjRZ8WCaeSM/CIKdoLw+29MNO6eqtchw0/vNvM8c9EkhrhMQKcY04OecVhmZkemFhd4SD5l92VX3z3xSxLkmazfNkj3CigWDXNxfDd2ORoGjA46Pga8RM=
 install: