Detecting when nush is accidentally run instead of nutest on a NuTestCase

nu.m.diff

diff --git a/objc/nu.m b/objc/nu.m
index 1d21a56..170206c 100644
--- a/objc/nu.m
+++ b/objc/nu.m
@@ -230,6 +230,12 @@ int NuMain(int argc, const char *argv[], const char *envp[])
        @catch (NuException* nuException)
     {
         printf("%s\n", [[nuException dump] cStringUsingEncoding:NSUTF8StringEncoding]);
+        if ([[nuException name] isEqualToString:@"NuUndefinedSuperclass"]) {
+            NSArray* a = [[nuException reason] componentsSeparatedByString:@" "];
+            if (([a count] == 3) && ([[a objectAtIndex:2] isEqualToString:@"NuTestCase"])) {
+                printf("Did you mean to use nutest instead of nush?\n");
+            }
+        }
        }
     @catch (id exception)
     {