Test using previous build platform for AppVeyor

Try fixing Python-related build failures in Cygwin build by using the previous version of the image, before the latest update.
2017-11-01 23:47:18 +01:00 · 2017-11-01 23:47:18 +01:00 · b05d864f5e
commit b05d864f5e
parent 80e2264373
1 changed files with 2 additions and 0 deletions
--- a/appveyor.yml
+++ b/appveyor.yml
@ -1,5 +1,7 @@
 version: '{build}'

+os: Previous Visual Studio 2015
+
 branches:
  only:
  - master