Disable flake8 for Python 2.6 on Travis

Since version 3.0.0, flake8 does not support Python 2.6, 3.2 and 3.3
anymore. It is still working for our Python 3.3 runs on Travis but
not for the Python 2.6 one so we only disable it for this version.

.travis.yml

@@ -8,16 +8,18 @@ before_install:
 install:
   # source because it sets up env vars on some platforms
   - source ci/travis/travis_install.sh
-script: ./run_tests.py
+script:
+  - ci/travis/travis_script.sh
 env:
   matrix:
-    - YCM_PYTHON_VERSION=2.7
-    - YCM_PYTHON_VERSION=2.6
-    - YCM_PYTHON_VERSION=3.3
+    - YCM_PYTHON_VERSION=2.7 YCM_FLAKE8=true
+    # Since 3.0.4, Flake8 is not working anymore on Python 2.6.
+    - YCM_PYTHON_VERSION=2.6 YCM_FLAKE8=false
+    - YCM_PYTHON_VERSION=3.3 YCM_FLAKE8=true
 matrix:
   exclude:
     - os: osx
-      env: YCM_PYTHON_VERSION=2.6
+      env: YCM_PYTHON_VERSION=2.6 YCM_FLAKE8=false
 addons:
   apt:
     sources:

ci/travis/travis_script.sh

@@ -0,0 +1,7 @@
+#!/bin/bash
+
+if [ "${YCM_FLAKE8}" = true ]; then
+  ./run_tests.py
+else
+  ./run_tests.py --no-flake8
+fi