Better error message for invalid argument to --category - silenced the printout of the raw args when not in verbose mode

git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@166514 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/dotest.py b/test/dotest.py
index 36678c2..965b046 100755
--- a/test/dotest.py
+++ b/test/dotest.py
@@ -409,7 +409,10 @@
 
     platform_system = platform.system()
     platform_machine = platform.machine()
-    print args
+    
+    # only print the args if being verbose
+    if args.v:
+        print args
 
     if args.h:
         do_help = True
@@ -425,7 +428,9 @@
     if args.categoriesList:
         for category in args.categoriesList:
             if not(category in validCategories):
-                print "fatal error: category '" + category + "' is not a valid category - edit dotest.py or correct your invocation"
+                print "fatal error: category '" + category + "' is not a valid category"
+                print "if you have added a new category, please edit dotest.py, adding your new category to validCategories"
+                print "else, please specify one or more of the following: " + str(validCategories.keys())
                 sys.exit(1)
         categoriesList = set(args.categoriesList)
         useCategories = True