Add try/catch for setting the process priority class, ignoring the exception if its message is "Success".

Author: asbjornu

src/GitTools.Core/GitTools.Core.Shared/Helpers/ProcessHelper.cs

@@ -24,11 +24,11 @@ public static Process Start(ProcessStartInfo startInfo)
                     try
                     {
                         process = Process.Start(startInfo);
-                        process.PriorityClass = ProcessPriorityClass.Idle;
                     }
                     catch (Win32Exception exception)
                     {
-                        // NOTE: https://msdn.microsoft.com/en-us/library/windows/desktop/ms681382%28v=vs.85%29.aspx?f=255&MSPPError=-2147217396 @asbjornu
+                        // NOTE: https://msdn.microsoft.com/en-us/library/windows/desktop/ms681382.aspx
+                        // -- @asbjornu
                         if (exception.NativeErrorCode == 2)
                         {
                             throw new FileNotFoundException(string.Format("The executable file '{0}' could not be found.",
@@ -39,6 +39,28 @@ public static Process Start(ProcessStartInfo startInfo)
 
                         throw;
                     }
+
+                    try
+                    {
+                        if (process != null)
+                        {
+                            process.PriorityClass = ProcessPriorityClass.Idle;
+                        }
+                    }
+                    catch (Win32Exception exception)
+                    {
+
+                        // NOTE: It seems like in some situations, setting the priority class will throw an exception
+                        // with the error code set to "Success", which I think we can safely interpret as a success and
+                        // not an exception.
+                        // See https://travis-ci.org/GitTools/GitVersion/jobs/171288284#L2026
+                        // and https://msdn.microsoft.com/en-us/library/windows/desktop/ms681382.aspx
+                        // -- @asbjornu
+                        if (exception.NativeErrorCode == 0)
+                        {
+                            throw;
+                        }
+                    }
                 }
             }
 
@@ -137,7 +159,7 @@ public struct ChangeErrorMode : IDisposable
             public ChangeErrorMode(ErrorModes mode)
             {
                 try
-                {
+                {
                     oldMode = SetErrorMode((int)mode);
                 }
                 catch (EntryPointNotFoundException)
@@ -150,7 +172,7 @@ public ChangeErrorMode(ErrorModes mode)
             void IDisposable.Dispose()
             {
                 try
-                {
+                {
                     SetErrorMode(oldMode);
                 }
                 catch (EntryPointNotFoundException)