Avoid using stdioType in unittest to work around issue 13712.

pkg/unittest/lib/vm_config.dart

Index: pkg/unittest/lib/vm_config.dart
diff --git a/pkg/unittest/lib/vm_config.dart b/pkg/unittest/lib/vm_config.dart
index 962ca9753b05fe47fc49d2961347a939e4843f0f..94e9ff0adee611a49df3d1c81814bd5dcad34a7a 100644
--- a/pkg/unittest/lib/vm_config.dart
+++ b/pkg/unittest/lib/vm_config.dart
@@ -21,8 +21,11 @@ class VMConfiguration extends SimpleConfiguration {
   // We make this public so the user can turn it off if they want.
   bool useColor;
 
-  VMConfiguration() :
-    super(), useColor = stdioType(stdout) == StdioType.TERMINAL;
+  VMConfiguration()
+      : super(),
+        // TODO(nweiz): Re-enable this when issue 13712 is fixed.
+        // useColor = stdioType(stdout) == StdioType.TERMINAL;
+        useColor = false;
 
   String formatResult(TestCase testCase) {
     String result = super.formatResult(testCase);