Add python38 test job for travis

.travis.yml

@@ -8,10 +8,6 @@ install:
   - make install
 jobs:
   include:
-    - stage: test
-      script:
-        - make test
-      python: '2.7'
     - stage: test
       script:
         - make test
@@ -25,8 +21,13 @@ jobs:
         - make test
       python: '3.7'
       dist: xenial
+    - stage: test
+      script:
+        - make test
+      python: '3.8'
+      dist: xenial
     - stage: coverage
-      python: '3.6'
+      python: '3.8'
       script:
         - make test
         - codecov --verbose