Make config parser extensible

This makes it possible to subclass the config parser, override it's
methods and then use this subclass when generating the CloudFormation
json. We need this so that bootstrap-salt can update the user data
section of the launch configuration.

CHANGELOG.md

@@ -1,7 +1,6 @@
-##UNRELEASED
-
-* Use a automatic resource naming to allow S3 bucket names to be auto named
-by AWS
+## Unreleased
+* Make it possible to override the ConfigParser so that sub-modules can update the CloudFormation config.
+* Use a automatic resource naming to allow S3 bucket names to be auto named by AWS
 
 ## Version 0.5.4
 

README.rst

@@ -304,6 +304,10 @@ If you wish to include some static cloudformation json and have it merged with t
 
 The tool will then perform a deep merge of the includes with the generated template dictionary. Any keys or subkeys in the template dictionary that clash will have their values **overwritten** by the included dictionary or recursively merged if the value is itself a dictionary.
 
+ConfigParser
+++++++++++++++
+If you want to include or modify cloudformation resources but need to include some logic and not a static include. You can subclass the ConfigParser and set the new class as `env.cloudformation_parser` in your fabfile.
+
 
 Enabling RDS encryption
 +++++++++++++++++++++++

bootstrap_cfn/config.py

@@ -43,7 +43,7 @@ def load_yaml(fp):
             return yaml.load(open(fp).read())
 
 
-class ConfigParser:
+class ConfigParser(object):
 
     config = {}
 

bootstrap_cfn/fab_tasks.py

@@ -271,7 +271,8 @@ def get_config():
         env.environment,
         passwords=env.stack_passwords)
 
-    cfn_config = ConfigParser(project_config.config, get_stack_name(), environment=env.environment, application=env.application)
+    Parser = env.get('cloudformation_parser', ConfigParser)
+    cfn_config = Parser(project_config.config, get_stack_name(), environment=env.environment, application=env.application)
     return cfn_config