Also force newer version of flake8, required by pytest-flake8 0.6.

.travis.yml

@@ -12,7 +12,7 @@ env:
  - LC_ALL=C LC_CTYPE=C
 script:
  # avoid VersionConflict when newer version is required
- - pip install -U pytest
+ - pip install -U pytest flake8
 
  # Output the env, because the travis docs just can't be trusted
  - env

appveyor.yml

@@ -12,5 +12,6 @@ install:
 build: off
 
 test_script:
+  - "python -m pip install -U flake8"
   - "python bootstrap.py"
   - "python setup.py test"