Ensure the installation process is finished

tools/internal_ci/helper_scripts/install_python38.ps1

@@ -13,8 +13,8 @@ function Install-Python {
         [string]$PythonInstallPath,
         [string]$PythonInstallerHash
     )
-    $PythonInstallerUrl = "https://www.python.org/ftp/python/$PythonVersion/$PythonInstaller"
-    $PythonInstallerPath = "C:\tools\$PythonInstaller"
+    $PythonInstallerUrl = "https://www.python.org/ftp/python/$PythonVersion/$PythonInstaller.exe"
+    $PythonInstallerPath = "C:\tools\$PythonInstaller.exe"
 
     # Downloads installer
     Write-Host "Downloading the Python installer: $PythonInstallerUrl => $PythonInstallerPath"
@@ -55,6 +55,22 @@ function Install-Python {
         Start-Sleep -Seconds 1
     }
 
+    # Waits until the installer process is gone
+    $ValidationStartTime = Get-Date
+    $EarlyExitDDL = $ValidationStartTime.addminutes(5)
+    While ($True) {
+        $CurrentTime = Get-Date
+        if ($CurrentTime -ge $EarlyExitDDL) {
+            throw "Python installation process hangs!"
+        }
+        $InstallProcess = Get-Process -Name $PythonInstaller
+        if ($InstallProcess -eq $null) {
+            Write-Host "Installation process exits normally."
+            break
+        }
+        Start-Sleep -Seconds 1
+    }
+
     # Installs pip
     & $PythonBinary -m ensurepip --user
 
@@ -63,7 +79,7 @@ function Install-Python {
 
 $Python38x86Config = @{
     PythonVersion = "3.8.0"
-    PythonInstaller = "python-3.8.0.exe"
+    PythonInstaller = "python-3.8.0"
     PythonInstallPath = "C:\Python38_32bit"
     PythonInstallerHash = "412a649d36626d33b8ca5593cf18318c"
 }
@@ -71,7 +87,7 @@ Install-Python @Python38x86Config
 
 $Python38x64Config = @{
     PythonVersion = "3.8.0"
-    PythonInstaller = "python-3.8.0-amd64.exe"
+    PythonInstaller = "python-3.8.0-amd64"
     PythonInstallPath = "C:\Python38"
     PythonInstallerHash = "29ea87f24c32f5e924b7d63f8a08ee8d"
 }