Add Python 3.8 to appveyor.yml

CHANGES.rst

@@ -7,7 +7,7 @@
 
 - Drop support for Python 3.4.
 
-- Add support for Python 3.8a3.
+- Add support for Python 3.8.
 
 - Properly declare dependency on zope.schema >= 4.2.0, introduced in
   zope.security 4.2.1.

appveyor.yml

@@ -13,11 +13,20 @@ environment:
     - python: 36-x64
     - python: 37
     - python: 37-x64
+    - python: 38
+    - python: 38-x64
     - { python: 27, PURE_PYTHON: 1 }
     - { python: 37, PURE_PYTHON: 1 }
 
 install:
   - "SET PATH=C:\\Python%PYTHON%;c:\\Python%PYTHON%\\scripts;%PATH%"
+  - ps: |
+      $env:PYTHON = "C:\\Python${env:PYTHON}"
+      if (-not (Test-Path $env:PYTHON)) {
+        curl -o install_python.ps1 https://raw.githubusercontent.com/matthew-brett/multibuild/11a389d78892cf90addac8f69433d5e22bfa422a/install_python.ps1
+        .\install_python.ps1
+      }
+  - ps: if (-not (Test-Path $env:PYTHON)) { throw "No $env:PYTHON" }
   - echo "C:\Program Files\Microsoft SDKs\Windows\v7.1\Bin\SetEnv.cmd" /x64 > "C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\bin\amd64\vcvars64.bat"
 # We need to install the C extensions that BTrees setup-requires
 # separately because we've seen problems with the BTrees build cleanup step trying
@@ -44,6 +53,6 @@ artifacts:
     name: wheel
 
 deploy_script:
-  - ps: if ($env:APPVEYOR_REPO_TAG -eq $TRUE -and $env:PURE_PYTHON -ne 1) { pip install twine; twine upload dist/* }
+  - ps: if ($env:APPVEYOR_REPO_TAG -eq $TRUE -and $env:PURE_PYTHON -ne 1) { pip install twine; twine upload --skip-existing dist/* }
 
 deploy: on