Explicitly create a conda environment for the test, specify Python version.

Author: arokem

appveyor.yml

@@ -35,6 +35,10 @@ install:
   - "python -c \"import struct; print(struct.calcsize('P') * 8)\""
 
   # Install the dependencies of the project.
+  - conda update -q conda
+  - conda info -a
+  - conda create -q -n test-environment python=%PYTHON_VERSION%
+  - activate test-environment
   - "conda install --yes --quiet numpy scipy matplotlib nose h5py"
   - "pip install pydicom"
   - "python setup.py install"