[CI] Happy workaround

- Install GHC
- Use cabal to install Happy
- force python version

appveyor.yml

@@ -139,6 +139,10 @@
 
             choco install haskell-stack -y
 
+            # temp workaround: install ghc for happy install
+
+            choco install ghc --version 8.0.1 -y
+
             choco install dotnetcore-sdk -y
 
             # choco install updated the path, so re-read them from the registry and reset $env:path
@@ -149,6 +153,12 @@
 
             $env:Path = "$machinePath;$userPath"
 
+            # temp workaround: run cabal update and install happy
+
+            cabal update
+
+            cabal install happy-1.19.5
+
             if ($env:BOND_BUILD -eq "Doc") {
 
                 choco install pandoc --version 1.19.2  -y
@@ -214,19 +224,27 @@
 
                 # Make sure we have Python27-64 before any other version
 
+                $env:Path = "C:\Python27\;${env:Path}"
+
                 if ($env:BOND_ARCH -eq 64) {
                     $env:Path = "C:\Python27-x64\scripts;C:\Python27-x64\;${env:Path}"
                 }
 
             }
 
+            if ($env:BOND_ARCH -eq 64) {
+
+                $pythonExt = "-x64"
+
+            }
+
             if ($env:BOND_BUILD -eq "Python") {
 
                 mkdir build
 
                 cd build
 
-                cmake "-DBoost_ADDITIONAL_VERSIONS=${env:BOND_BOOST}" $cmakeFlags -G $cmakeGenerator ..
+                cmake "-DBoost_ADDITIONAL_VERSIONS=${env:BOND_BOOST}" "-DPYTHON_EXECUTABLE:FILEPATH=C:\Python27${pythonExt}\python.exe" $cmakeFlags -G $cmakeGenerator ..
 
             }
 
@@ -246,7 +264,7 @@
 
                 cd build
 
-                cmake $cmakeFlags -G $cmakeGenerator .. 2>cmake_stderr.log
+                cmake "-DPYTHON_EXECUTABLE:FILEPATH=C:\Python27${pythonExt}\python.exe" $cmakeFlags -G $cmakeGenerator .. 2>cmake_stderr.log
 
                 Get-Content cmake_stderr.log