fix py2.7

Author: rusty1s

.travis.yml

@@ -23,6 +23,7 @@ install:
   - pip install pycodestyle
   - pip install flake8
   - pip install codecov
+  - if [[ $TRAVIS_PYTHON_VERSION == 2.7 ]]; then pip install "pytest<5.0"; fi
 script:
   - if [[ $TRAVIS_PYTHON_VERSION != 2.7 ]]; then pycodestyle .; fi
   - if [[ $TRAVIS_PYTHON_VERSION != 2.7 ]]; then flake8 .; fi

setup.py

@@ -25,11 +25,7 @@
 
 install_requires = []
 setup_requires = ['pytest-runner']
-tests_require = [
-    'pytest<5.0;python_version<"3.0"',
-    'pytest;python_version>="3.0"',
-    'pytest-cov',
-]
+tests_require = ['pytest', 'pytest-cov']
 
 setup(
     name='torch_scatter',