New valid_length and fix valid_range

- New valid_length function
- Also fixed some errors in valid_range

Change-Id: I1a9856ee796388d189060f9b860cd88ff3e9e16c
Signed-off-by: Michael Walsh <micwalsh@us.ibm.com>
diff --git a/lib/gen_robot_valid.py b/lib/gen_robot_valid.py
index 556561d..160da0c 100755
--- a/lib/gen_robot_valid.py
+++ b/lib/gen_robot_valid.py
@@ -214,6 +214,14 @@
     process_error_message(error_message)
 
 
+def valid_length(var_name, *args, **kwargs):
+
+    var_value, args, kwargs = valid_init(var_name, *args, **kwargs)
+    error_message = \
+        gv.valid_length(var_value, *args, var_name=var_name, **kwargs)
+    process_error_message(error_message)
+
+
 # Modify the validation function docstrings by calling customize_doc_string
 # for each function in the func_names list.
 func_names = [