ec2_vpc_igw: fix NoneType error (ansible-collections#695)

`ec2_vpc_igw`: fix NoneType error

SUMMARY

use paginator for describe internet gateways and add retry_codes='InvalidInternetGatewayID.NotFound' (thanks @alinabuzachis)
Fixes ansible-collections#647

ISSUE TYPE

Bugfix Pull Request

COMPONENT NAME
ec2_vpc_igw
ADDITIONAL INFORMATION

previously added InternetGatewayAttached waiter but problem still persists (ansible-collections#691)

Reviewed-by: Abhijeet Kasurde <None>
Reviewed-by: Jill R <None>

changelogs/fragments/695-ec2_vpc_igw-fix-nonetype-with-paginator.yml

@@ -0,0 +1,2 @@
+bugfixes:
+  - ec2_vpc_igw - use paginator for describe internet gateways and add retry to fix NoneType object is not subscriptable error (https://github.com/ansible-collections/amazon.aws/pull/695).

plugins/modules/ec2_vpc_igw.py

@@ -112,6 +112,12 @@
 from ..module_utils.tagging import boto3_tag_list_to_ansible_dict
 
 
+@AWSRetry.jittered_backoff(retries=10, delay=10)
+def describe_igws_with_backoff(connection, **params):
+    paginator = connection.get_paginator('describe_internet_gateways')
+    return paginator.paginate(**params).build_full_result()['InternetGateways']
+
+
 class AnsibleEc2Igw():
 
     def __init__(self, module, results):
@@ -135,10 +141,8 @@ def process(self):
 
     def get_matching_igw(self, vpc_id):
         filters = ansible_dict_to_boto3_filter_list({'attachment.vpc-id': vpc_id})
-        igws = []
         try:
-            response = self._connection.describe_internet_gateways(aws_retry=True, Filters=filters)
-            igws = response.get('InternetGateways', [])
+            igws = describe_igws_with_backoff(self._connection, Filters=filters)
         except (botocore.exceptions.ClientError, botocore.exceptions.BotoCoreError) as e:
             self._module.fail_json_aws(e)
 
@@ -211,17 +215,20 @@ def ensure_igw_present(self, vpc_id, tags, purge_tags):
                 # Ensure the gateway is attached before proceeding
                 waiter = get_waiter(self._connection, 'internet_gateway_attached')
                 waiter.wait(InternetGatewayIds=[igw['internet_gateway_id']])
-
                 self._results['changed'] = True
             except botocore.exceptions.WaiterError as e:
                 self._module.fail_json_aws(e, msg="No Internet Gateway exists.")
             except (botocore.exceptions.ClientError, botocore.exceptions.BotoCoreError) as e:
                 self._module.fail_json_aws(e, msg='Unable to create Internet Gateway')
 
+        # Modify tags
         self._results['changed'] |= ensure_ec2_tags(
             self._connection, self._module, igw['internet_gateway_id'],
-            resource_type='internet-gateway', tags=tags, purge_tags=purge_tags
+            resource_type='internet-gateway', tags=tags, purge_tags=purge_tags,
+            retry_codes='InvalidInternetGatewayID.NotFound'
         )
+
+        # Update igw
         igw = self.get_matching_igw(vpc_id)
         igw_info = self.get_igw_info(igw, vpc_id)
         self._results.update(igw_info)