Add optional schema compiler error messages

tools/json_schema_compiler/model.py

Index: tools/json_schema_compiler/model.py
diff --git a/tools/json_schema_compiler/model.py b/tools/json_schema_compiler/model.py
index d6b6efc1a12f3519777d08b4995fa43d27e8c8ea..b74e3832cc7a9d828672482b52ac2e849b3cb468 100644
--- a/tools/json_schema_compiler/model.py
+++ b/tools/json_schema_compiler/model.py
@@ -51,6 +51,7 @@ class Namespace(object):
   - |properties| a map of property names to their model.Property
   - |compiler_options| the compiler_options dict, only present if
                        |include_compiler_options| is True
+  - |generate_error_messages| if error messages should be generated
   """
   def __init__(self, json, source_file, include_compiler_options=False):
     self.name = json['namespace']
@@ -66,6 +67,7 @@ class Namespace(object):
     self.properties = _GetProperties(self, json, self, toplevel_origin)
     if include_compiler_options:
       self.compiler_options = json.get('compiler_options', {})
+    self.generate_error_messages = json.get('generate_error_messages', False)
 
 class Origin(object):
   """Stores the possible origin of model object as a pair of bools. These are: