(GH-707) Exit with specific exit codes

When running PowerShell and certain things are found, exit
appropriately.

- When a file is not found, exit 2.
- When a file found is not right, exit 4.
- When a file can not be downloaded, exit 404.
- When unzipping has issues, exit with its result exit code

src/chocolatey.resources/helpers/functions/Get-ChocolateyUnzip.ps1

@@ -138,6 +138,7 @@ param(
   Unregister-Event -SourceIdentifier "LogErrors_ChocolateyZipProc"
 
   $exitCode = $process.ExitCode
+  Set-PowerShellExitCode $exitCode
   $process.Dispose()
   Write-Debug "Command ['$7zip' $params] exited with `'$exitCode`'."
 

src/chocolatey.resources/helpers/functions/Get-WebFile.ps1

@@ -222,6 +222,7 @@ param(
       [GC]::Collect()
     }
 
+    Set-PowerShellExitCode 404
     throw "The remote file either doesn't exist, is unauthorized, or is forbidden for url '$url'. $($_.Exception.Message)"
   } finally {
     if ($res -ne $null) {

src/chocolatey.resources/helpers/functions/Start-ChocolateyProcessAsAdmin.ps1

@@ -61,9 +61,15 @@ Elevating Permissions and running [`"$exeToRun`" $wrappedStatements]. This may t
 
   $exeIsTextFile = [System.IO.Path]::GetFullPath($exeToRun) + ".istext"
   if (([System.IO.File]::Exists($exeIsTextFile))) {
+    Set-PowerShellExitCode 4
     throw "The file was a text file but is attempting to be run as an executable - '$exeToRun'"
   }
 
+  if (!([System.IO.File]::Exists($exeToRun))) {
+    Set-PowerShellExitCode 2
+    throw "Could not find '$exeToRun'"
+  }
+
   # Redirecting output slows things down a bit.
   $writeOutput = {
     if ($EventArgs.Data -ne $null) {