drop python2 support

 - remove python2 from the .travis.yaml file
 - remove python2 from the tox.ini file
 - remove `-y` flag from isort command in update-pycodestle.sh script
 - add update-pycodestyle, coverage & codecov tests for python3

Signed-off-by: Priyanka Saggu <priyankasaggu11929@gmail.com>

.travis.yml

@@ -18,16 +18,12 @@ jobs:
       script: ./hack/verify-boilerplate.sh
       python: 3.7
     - stage: test
-      python: 2.7
-      env: TOXENV=py27
-    - python: 2.7
-      env: TOXENV=py27-functional
-    - python: 2.7
+      python: 3.9
       env: TOXENV=update-pycodestyle
+    - python: 3.9
+      env: TOXENV=coverage,codecov
     - python: 3.7
       env: TOXENV=docs
-    - python: 2.7
-      env: TOXENV=coverage,codecov
     - python: 3.5
       env: TOXENV=py35
     - python: 3.5

tox.ini

@@ -1,8 +1,8 @@
 [tox]
 skipsdist = True
 envlist =
-   py27, py3{5,6,7,8,9}
-   py27-functional, py3{5,6,7,8,9}-functional
+   py3{5,6,7,8,9}
+   py3{5,6,7,8,9}-functional
 
 [testenv]
 passenv = TOXENV CI TRAVIS TRAVIS_*