Updated pytest dependency

Author: syrusakbary

.travis.yml

@@ -22,7 +22,7 @@ before_install:
       fi
 install:
 - pip install pytest-cov pytest-mock coveralls flake8 isort==3.9.6 gevent==1.1b5 six>=1.10.0 promise>=0.4.2 pytest-benchmark
-- pip install pytest --upgrade
+- pip install pytest==2.9.2
 - pip install -e .
 script:
 - flake8

setup.py

@@ -48,7 +48,7 @@
         'promise>=0.4.2'
     ],
     tests_require=[
-        'pytest',
+        'pytest==2.9.2',
         'pytest-benchmark',
         'pytest-cov',
         'gevent==1.1rc1',