Skip deploy job on Travis if we are not on a tag

.travis.yml

@@ -25,6 +25,11 @@ env:
 install: pip install tox setuptools_scm
 script: tox
 
+stages:
+- test
+- name: deploy
+  if: repo = pytest-dev/pytest-xdist AND tag IS present
+
 jobs:
   include:
     - stage: test