Install conda on appveyor

appveyor.yml

@@ -1,7 +1,10 @@
 environment:
-  PYTHON: "C:\\Miniconda36-x64"
+  PYTHON_ARCH: "64"
+  PYTHON: "C:\\Python36-conda64"
 
 install:
+  # Install miniconda Python
+  - "powershell ./ci/install_python.ps1"
    # Prepend newly installed Python to the PATH of this build (this cannot be
   # done from inside the powershell script as it would require to restart
   # the parent CMD process).

ci/install_python.ps1

@@ -0,0 +1,99 @@
+# Sample script to install Python and pip under Windows
+# Authors: Olivier Grisel, Jonathan Helmus and Kyle Kastner
+# License: CC0 1.0 Universal: http://creativecommons.org/publicdomain/zero/1.0/
+
+# copied Jan, 16th from https://github.com/pydata/xarray/blob/master/ci/install_python.ps1
+
+$MINICONDA_URL = "http://repo.continuum.io/miniconda/"
+$BASE_URL = "https://www.python.org/ftp/python/"
+
+
+function DownloadMiniconda ($python_version, $platform_suffix) {
+    $webclient = New-Object System.Net.WebClient
+    if ($python_version -match "3.[456]") {
+        $filename = "Miniconda3-latest-Windows-" + $platform_suffix + ".exe"
+    } else {
+        $filename = "Miniconda-latest-Windows-" + $platform_suffix + ".exe"
+    }
+    $url = $MINICONDA_URL + $filename
+
+    $basedir = $pwd.Path + "\"
+    $filepath = $basedir + $filename
+    if (Test-Path $filename) {
+        Write-Host "Reusing" $filepath
+        return $filepath
+    }
+
+    # Download and retry up to 3 times in case of network transient errors.
+    Write-Host "Downloading" $filename "from" $url
+    $retry_attempts = 2
+    for($i=0; $i -lt $retry_attempts; $i++){
+        try {
+            $webclient.DownloadFile($url, $filepath)
+            break
+        }
+        Catch [Exception]{
+            Start-Sleep 1
+        }
+   }
+   if (Test-Path $filepath) {
+       Write-Host "File saved at" $filepath
+   } else {
+       # Retry once to get the error message if any at the last try
+       $webclient.DownloadFile($url, $filepath)
+   }
+   return $filepath
+}
+
+
+function InstallMiniconda ($python_version, $architecture, $python_home) {
+    Write-Host "Installing Python" $python_version "for" $architecture "bit architecture to" $python_home
+    if (Test-Path $python_home) {
+        Write-Host $python_home "already exists, skipping."
+        return $false
+    }
+    if ($architecture -match "32") {
+        $platform_suffix = "x86"
+    } else {
+        $platform_suffix = "x86_64"
+    }
+
+    $filepath = DownloadMiniconda $python_version $platform_suffix
+    Write-Host "Installing" $filepath "to" $python_home
+    $install_log = $python_home + ".log"
+    $args = "/S /D=$python_home"
+    Write-Host $filepath $args
+    Start-Process -FilePath $filepath -ArgumentList $args -Wait -Passthru
+    if (Test-Path $python_home) {
+        Write-Host "Python $python_version ($architecture) installation complete"
+    } else {
+        Write-Host "Failed to install Python in $python_home"
+        Get-Content -Path $install_log
+        Exit 1
+    }
+}
+
+
+function InstallCondaPackages ($python_home, $spec) {
+    $conda_path = $python_home + "\Scripts\conda.exe"
+    $args = "install --yes " + $spec
+    Write-Host ("conda " + $args)
+    Start-Process -FilePath "$conda_path" -ArgumentList $args -Wait -Passthru
+}
+
+function UpdateConda ($python_home) {
+    $conda_path = $python_home + "\Scripts\conda.exe"
+    Write-Host "Updating conda..."
+    $args = "update --yes conda"
+    Write-Host $conda_path $args
+    Start-Process -FilePath "$conda_path" -ArgumentList $args -Wait -Passthru
+}
+
+
+function main () {
+    InstallMiniconda $env:PYTHON_VERSION $env:PYTHON_ARCH $env:PYTHON
+    UpdateConda $env:PYTHON
+    InstallCondaPackages $env:PYTHON "conda-build jinja2 anaconda-client"
+}
+
+main