Cleanup - use is_boto3_error_(message|code) (ansible-collections#268)

* Reorder imports
* Make use of is_boto3_error_message
* Mass-migration over to is_boto3_error_code
* Remove unused imports
* unused vars in exception
* Improve consistency around catching BotoCoreError and ClientError
* Remove unused imports
* Remove unused 'PolicyError' from iam_policy_info
* Avoid catching botocore.exceptions.ClientError when we only want some error codes
* Import camel_dict_to_snake_dict/snake_dict_to_camel_dict from ansible.module_utils.common.dict_transformations

This commit was initially merged in https://github.com/ansible-collections/community.aws
See: ansible-collections/community.aws@4cf52ef

plugins/modules/ec2_transit_gateway_info.py

@@ -165,17 +165,17 @@
 '''
 
 try:
-    from botocore.exceptions import BotoCoreError, ClientError
+    import botocore
 except ImportError:
     pass  # handled by imported AnsibleAWSModule
 
+from ansible.module_utils.common.dict_transformations import camel_dict_to_snake_dict
+
 from ansible_collections.amazon.aws.plugins.module_utils.core import AnsibleAWSModule
-from ansible_collections.amazon.aws.plugins.module_utils.ec2 import (
-    AWSRetry,
-    boto3_tag_list_to_ansible_dict,
-    camel_dict_to_snake_dict,
-    ansible_dict_to_boto3_filter_list
-)
+from ansible_collections.amazon.aws.plugins.module_utils.core import is_boto3_error_code
+from ansible_collections.amazon.aws.plugins.module_utils.ec2 import AWSRetry
+from ansible_collections.amazon.aws.plugins.module_utils.ec2 import ansible_dict_to_boto3_filter_list
+from ansible_collections.amazon.aws.plugins.module_utils.ec2 import boto3_tag_list_to_ansible_dict
 
 
 class AnsibleEc2TgwInfo(object):
@@ -208,11 +208,9 @@ def describe_transit_gateways(self):
         try:
             response = self._connection.describe_transit_gateways(
                 TransitGatewayIds=transit_gateway_ids, Filters=filters)
-        except ClientError as e:
-            if e.response['Error']['Code'] == 'InvalidTransitGatewayID.NotFound':
-                self._results['transit_gateways'] = []
-                return
-            raise
+        except is_boto3_error_code('InvalidTransitGatewayID.NotFound'):
+            self._results['transit_gateways'] = []
+            return
 
         for transit_gateway in response['TransitGateways']:
             transit_gateway_info.append(camel_dict_to_snake_dict(transit_gateway, ignore_list=['Tags']))
@@ -253,7 +251,7 @@ def main():
     tgwf_manager = AnsibleEc2TgwInfo(module=module, results=results)
     try:
         tgwf_manager.describe_transit_gateways()
-    except (BotoCoreError, ClientError) as e:
+    except (botocore.exceptions.ClientError, botocore.exceptions.BotoCoreError) as e:
         module.fail_json_aws(e)
 
     module.exit_json(**results)