more descriptive variable name

Signed-off-by: Mikael Arguedas <mikael.arguedas@gmail.com>

Author: mikaelarguedas

rosidl_generator_py/resource/_idl.py.em

@@ -19,11 +19,11 @@ import_statements = set()
 @#######################################################################
 @{
 from rosidl_parser.definition import Message
-msg_required_import_imported = False
+rosidl_parser_definition_imported = False
 }@
 @[for message in content.get_elements_of_type(Message)]@
-@[  if not msg_required_import_imported]@
-@{msg_required_import_imported = True}@
+@[  if not rosidl_parser_definition_imported]@
+@{rosidl_parser_definition_imported = True}@
 import rosidl_parser.definition
 @[  end if]@
 @{
@@ -41,8 +41,8 @@ TEMPLATE(
 from rosidl_parser.definition import Service
 }@
 @[for service in content.get_elements_of_type(Service)]@
-@[  if not msg_required_import_imported]@
-@{msg_required_import_imported = True}@
+@[  if not rosidl_parser_definition_imported]@
+@{rosidl_parser_definition_imported = True}@
 import rosidl_parser.definition
 @[  end if]@
 @{
@@ -60,8 +60,8 @@ TEMPLATE(
 from rosidl_parser.definition import Action
 }@
 @[for action in content.get_elements_of_type(Action)]@
-@[  if not msg_required_import_imported]@
-@{msg_required_import_imported = True}@
+@[  if not rosidl_parser_definition_imported]@
+@{rosidl_parser_definition_imported = True}@
 import rosidl_parser.definition
 @[  end if]@
 @{