CI: Do not install from requirements in lint stage

Author: ayan-b

templates/travis.yml.jj2

@@ -23,11 +23,24 @@ python:
 stages:
   - test
   - lint
+
+.disable_global: &disable_global
+  before_install: false
+  install: true
+  before_script: false
+  after_success: false
+  after_failure: false
+
+.lint: &lint
+  <<: *disable_global
+  python: 3.6
+  stage: lint
+  install: pip install flake8
+  script: flake8
+
 jobs:
   include:
-    - stage: lint
-      python: 3.6
-      script: make lint
+    - *lint
 
 stage: test
 
@@ -36,7 +49,6 @@ script: make test
 before_install:
 {% block custom_install %}
 {% endblock%}
-  - if [[ $TRAVIS_PYTHON_VERSION == "2.6" ]]; then pip install flake8==2.6.2; fi
   - if [[ -f min_requirements.txt && "$MINREQ" -eq 1 ]]; then
       mv min_requirements.txt requirements.txt ;
     fi