Improve "JSON not properly formatted" error message to say how to fix it (#59)

tests.py

@@ -29,7 +29,8 @@ def validate(path):
                     outfile.write(pretty)
                 print("    %sJSON in %s has been fixed.%s" % (YELLOW, path, END))
             else:
-                print("    %sJSON in %s is NOT properly formatted.%s" % (YELLOW, path, END))
+                print("    %sJSON in %s is NOT properly formatted! This is really easy to fix!"
+                      " just run tests.py --clean.%s" % (YELLOW, path, END))
                 formatting = False
         hosts = peers.keys()
         for host in hosts: