travis: fixed deployment, remove 3.9-dev for now

.travis.yml

@@ -1,10 +1,14 @@
+stages:
+  - name: test
+    if: tag IS blank
+  - name: deploy
+    if: tag IS present
 language: python
 python:
 - '3.8'
 - '3.7'
 - '3.6'
 - '3.5'
-- 3.9-dev
 - 3.8-dev
 - 3.7-dev
 - 3.6-dev
@@ -24,12 +28,13 @@ notifications:
   email:
     on_success: change
     on_failure: change
-if: branch != master
 jobs:
   include:
     - stage: deploy
-      python: 3.8
-      if: branch = master
+      python: '3.8'
+      env: GEVENT=false
+      script: skip
+      install: skip
       deploy:
         provider: pypi
         user: __token__