Use stages in travis to have deployment depend on success in all Python versions.

.travis.yml

@@ -1,23 +1,32 @@
+dist: trusty
 sudo: false
 language: python
-python:
+
-- 2.7
+jobs:
-- 3.6
+  fast_finish: true
-install:
+  include:
-- pip install tox "setuptools>=28.2"
+  - python: 2.7
-script:
+  - python: &latest_py3 3.6
-- tox
+  - stage: deploy
-branches:
+    if: tag IS present
-  except:
+    python: *latest_py3
-  - skeleton
+    install: skip
+    script: skip
+    before_deploy: python bootstrap.py
     deploy:
       provider: pypi
-  server: https://upload.pypi.org/legacy/
       on:
         tags: true
         all_branches: true
-    python: 3.6
       user: jaraco
       # supply password with `travis encrypt --add deploy.password`
       distributions: dists
+      skip_cleanup: true
       skip_upload_docs: true
+
+cache: pip
+
+install:
+- pip install tox
+
+script: tox