install additional pytest packages

Author: mfeurer

appveyor.yml

@@ -35,8 +35,10 @@ install:
 
   # Install the build and runtime dependencies of the project.
   - "cd C:\\projects\\openml-python"
-  - conda install --quiet --yes scikit-learn=0.20.0 nb_conda nb_conda_kernels numpy scipy pytest requests nbformat python-dateutil nbconvert pandas matplotlib seaborn
+  - conda install --quiet --yes scikit-learn=0.20.0 nb_conda nb_conda_kernels numpy scipy requests nbformat python-dateutil nbconvert pandas matplotlib seaborn
   - pip install liac-arff xmltodict oslo.concurrency
+  # Packages for (parallel) unit tests with pytest
+  - pip install pytest pytest-xdist pytest-timeout
   - "pip install .[test]"