Ensure we don't use ANSI color codes in MSpec tests

MSpec outputs the results to HTML/XML and 0x1B is not a valid character

src/test/Test.FAKECore/FSIHelperSpecs.cs

@@ -3,6 +3,7 @@
 using System.Linq;
 using System.Text;
 using System.IO;
+using System.Text.RegularExpressions;
 using Fake;
 using Machine.Specifications;
 using Messages = Microsoft.FSharp.Collections.FSharpList<Fake.ProcessHelper.ConsoleMessage>;
@@ -121,6 +122,21 @@ static FSIHelper.Script script(string path, string contents)
             return new FSIHelper.Script(contents, path.Replace("\\", "/"), null, null);
         }
 
+        private Establish context = () =>
+        {
+            var consoleListener = TraceListener.defaultConsoleTraceListener;
+
+            if (consoleListener.useAnsiColorCodes)
+            {
+                TraceListener.listeners.Remove(consoleListener);
+                TraceListener.listeners.Add(
+                    new TraceListener.ConsoleTraceListener(
+                        consoleListener.importantMessagesToStdErr,
+                        consoleListener.colorMap,
+                        useAnsiColorCodes: false));
+            }
+        };
+
         It fallback_should_not_trigger_when_attribute_constructor_throws =
             () =>
             {