Ensure ANSI is disabled in TracerTest regardless of environment (issue #1103)

Author: dwalluck

src/test/java/picocli/TracerTest.java

@@ -2,6 +2,7 @@
 
 import org.junit.Rule;
 import org.junit.Test;
+import org.junit.contrib.java.lang.system.ProvideSystemProperty;
 import org.junit.contrib.java.lang.system.RestoreSystemProperties;
 import org.junit.rules.TestRule;
 
@@ -23,6 +24,9 @@ public class TracerTest {
     @Rule
     public final TestRule restoreSystemProperties = new RestoreSystemProperties();
 
+    @Rule
+    public final ProvideSystemProperty ansiOFF = new ProvideSystemProperty("picocli.ansi", "false");
+
     private static void clearBuiltInTracingCache() throws Exception {
         Field field = Class.forName("picocli.CommandLine$BuiltIn").getDeclaredField("traced");
         field.setAccessible(true);