Force later pytest

.travis.yml

@@ -10,6 +10,9 @@ env:
  - LC_ALL=C
  - ""
 script:
+ # avoid VersionConflict when newer version is required
+ - python -m pip install -U pytest
+
  # update egg_info based on setup.py in checkout
  - python bootstrap.py
 

setup.py

@@ -159,7 +159,7 @@ setup_params = dict(
     scripts=[],
     tests_require=[
         'setuptools[ssl]',
-        'pytest',
+        'pytest>=2.8',
     ] + (['mock'] if sys.version_info[:2] < (3, 3) else []),
     setup_requires=[
     ] + sphinx + pytest_runner,