Install flake8 before trying to use it in gate

Signed-off-by: Robbie Harwood <rharwood@redhat.com>

Author: frozencemetery

.travis.yml

@@ -1,12 +1,18 @@
+sudo: required
+
 language: python
 python:
     - "2.6"
     - "2.7"
     - "3.4"
     - "3.6"
 
+before_install:
+  - sudo apt-get update -qq
+  - sudo apt-get install flake8
+
 install:
-    - pip install .
+  - pip install .
 
 script:
   - flake8