Update .travis.yml

.travis.yml

@@ -1,9 +1,9 @@
 language: python
 cache: pip
 python:
-- '3.5'
 - '3.6'
 - '3.7'
+- '3.8'
 install:
 - pip install -r test-requirements.txt -U
 services:
@@ -27,4 +27,4 @@ deploy:
     secure: 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
   on:
     tags: true
-    python: '3.7'
+    python: '3.8'