TST: Use already installed in Appveyor Python

Author: Kojoley

appveyor.yml

@@ -9,42 +9,16 @@ environment:
     CMD_IN_ENV: "cmd /E:ON /V:ON /C .\\ci\\appveyor\\run_with_env.cmd"
 
   matrix:
-     - PYTHON: "C:\\Python27_32"
-       PYTHON_VERSION: "2.7.14"
-       PYTHON_ARCH: "32"
-
-     - PYTHON: "C:\\Python27_64"
-       PYTHON_VERSION: "2.7.14"
-       PYTHON_ARCH: "64"
-
-     - PYTHON: "C:\\Python34_32"
-       PYTHON_VERSION: "3.4.4"
-       PYTHON_ARCH: "32"
-
-     - PYTHON: "C:\\Python34_64"
-       PYTHON_VERSION: "3.4.4"
-       PYTHON_ARCH: "64"
-
-     - PYTHON: "C:\\Python35_32"
-       PYTHON_VERSION: "3.5.4"
-       PYTHON_ARCH: "32"
-
-     - PYTHON: "C:\\Python35_64"
-       PYTHON_VERSION: "3.5.4"
-       PYTHON_ARCH: "64"
-
-     - PYTHON: "C:\\Python36_32"
-       PYTHON_VERSION: "3.6"
-       PYTHON_ARCH: "32"
-
-     - PYTHON: "C:\\Python36_64"
-       PYTHON_VERSION: "3.6"
-       PYTHON_ARCH: "64"
+     - PYTHON: "C:\\Python27"
+     - PYTHON: "C:\\Python27-x64"
+     - PYTHON: "C:\\Python34"
+     - PYTHON: "C:\\Python34-x64"
+     - PYTHON: "C:\\Python35"
+     - PYTHON: "C:\\Python35-x64"
+     - PYTHON: "C:\\Python36"
+     - PYTHON: "C:\\Python36-x64"
 
 install:
-  # Install Python (from the official .msi of https://python.org) and pip when
-  # not already installed.
-  - "powershell ./ci/appveyor/install.ps1"
   - "SET PATH=%PYTHON%;%PYTHON%\\Scripts;%PATH%"
 
   # Check that we have the expected version and architecture for Python