testing pycodestyle with python3

Author: Priyankasaggu11929

.travis.yml

@@ -24,7 +24,9 @@ jobs:
       [[ "${TRAVIS_TAG}" =~ ^v[0-9]+\.[0-9]+\.[0-9]+(([ab]|dev|rc)[0-9]+)?$ ]]
 
   - stage: test
-    python: 3.7
+    python: 3.9
+    env: TOXENV=update-pycodestyle    
+  - python: 3.7
     env: TOXENV=docs
   - python: 3.5
     env: TOXENV=py35