Raise better exception on InvalidParameterValue error

There are several reasons why we might get an `InvalidParameterValue`
from the SES API. One, as correctly identified before in
https://github.com/alphagov/notifications-api/pull/713/files
is if we allow an email address on our side that SES rejects.

However, there are other types of errors that could cause an
`InvalidParameterValue`. One example is a `Header too long: 'Subject'`
error that we have seen happen in production. This shouldn't raise an
`InvalidEmailError` as that is not appropriate.

Therefore, we introduce a new exception
`EmailClientNonRetryableException`, that represents any exception back
from an email client that we can use whenever we get a
`InvalidParameterValue` error.

Note, I chose `EmailClientNonRetryableException` rather than
`SESClientNonRetryableException` as our code needs to catch this
exception and it shouldn't be aware of what email client is being used,
it just needs to know that it came from one of the email clients (if in
time we have more than one).

In time, we may wish to extend the approach of having generic
`EmailClient` exceptions and `SMSClient` exceptions as this should be
the most extendable pattern and a good abstraction.

app/celery/provider_tasks.py

@@ -1,10 +1,10 @@
 from flask import current_app
-from notifications_utils.recipients import InvalidEmailError
 from notifications_utils.statsd_decorators import statsd
 from sqlalchemy.orm.exc import NoResultFound
 
 from app import notify_celery
 from app.config import QueueNames
+from app.clients.email import EmailClientNonRetryableException
 from app.clients.email.aws_ses import AwsSesClientThrottlingSendRateException
 from app.dao import notifications_dao
 from app.dao.notifications_dao import update_notification_status_by_id
@@ -47,7 +47,7 @@ def deliver_email(self, notification_id):
         if not notification:
             raise NoResultFound()
         send_to_providers.send_email_to_provider(notification)
-    except InvalidEmailError as e:
+    except EmailClientNonRetryableException as e:
         current_app.logger.exception(e)
         update_notification_status_by_id(notification_id, 'technical-failure')
     except Exception as e:

app/clients/email/__init__.py

@@ -8,6 +8,18 @@ class EmailClientException(ClientException):
     pass
 
 
+class EmailClientNonRetryableException(ClientException):
+    '''
+    Represents an error returned from the email client API with a 4xx response code
+    that should not be retried and should instead be marked as technical failure.
+    An example of this would be an email address that makes it through our
+    validation rules but is rejected by SES. There is no point in retrying this type as
+    it will always fail however many calls to SES. Whereas a throttling error would not
+    use this exception as it may succeed if we retry
+    '''
+    pass
+
+
 class EmailClient(Client):
     '''
     Base Email client for sending emails.

app/clients/email/aws_ses.py

@@ -5,7 +5,7 @@ from time import monotonic
 from notifications_utils.recipients import InvalidEmailError
 
 from app.clients import STATISTICS_DELIVERED, STATISTICS_FAILURE
-from app.clients.email import (EmailClientException, EmailClient)
+from app.clients.email import EmailClient, EmailClientException, EmailClientNonRetryableException
 
 ses_response_map = {
     'Permanent': {
@@ -122,7 +122,7 @@ class AwsSesClient(EmailClient):
 
             # http://docs.aws.amazon.com/ses/latest/DeveloperGuide/api-error-codes.html
             if e.response['Error']['Code'] == 'InvalidParameterValue':
-                raise InvalidEmailError(str(e))
+                raise EmailClientNonRetryableException(str(e))
             elif (
                 e.response['Error']['Code'] == 'Throttling'
                 and e.response['Error']['Message'] == 'Maximum sending rate exceeded.'

tests/app/celery/test_provider_tasks.py

@@ -1,11 +1,11 @@
 import pytest
 from botocore.exceptions import ClientError
 from celery.exceptions import MaxRetriesExceededError
-from notifications_utils.recipients import InvalidEmailError
 
 import app
 from app.celery import provider_tasks
 from app.celery.provider_tasks import deliver_sms, deliver_email
+from app.clients.email import EmailClientNonRetryableException
 from app.clients.email.aws_ses import AwsSesClientException, AwsSesClientThrottlingSendRateException
 from app.exceptions import NotificationTechnicalFailureException
 
@@ -93,8 +93,11 @@ def test_should_go_into_technical_error_if_exceeds_retries_on_deliver_email_task
     assert sample_notification.status == 'technical-failure'
 
 
-def test_should_technical_error_and_not_retry_if_invalid_email(sample_notification, mocker):
-    mocker.patch('app.delivery.send_to_providers.send_email_to_provider', side_effect=InvalidEmailError('bad email'))
+def test_should_technical_error_and_not_retry_if_EmailClientNonRetryableException(sample_notification, mocker):
+    mocker.patch(
+        'app.delivery.send_to_providers.send_email_to_provider',
+        side_effect=EmailClientNonRetryableException('bad email')
+    )
     mocker.patch('app.celery.provider_tasks.deliver_email.retry')
 
     deliver_email(sample_notification.id)

tests/app/clients/test_aws_ses.py

@@ -1,9 +1,9 @@
 import botocore
 import pytest
 from unittest.mock import Mock, ANY
-from notifications_utils.recipients import InvalidEmailError
 
 from app import aws_ses_client
+from app.clients.email import EmailClientNonRetryableException
 from app.clients.email.aws_ses import get_aws_responses, AwsSesClientException, AwsSesClientThrottlingSendRateException
 
 
@@ -91,7 +91,7 @@ def test_send_email_handles_punycode_to_address(notify_api, mocker):
     )
 
 
-def test_send_email_raises_bad_email_as_InvalidEmailError(mocker):
+def test_send_email_raises_invalid_parameter_value_error_as_EmailClientNonRetryableException(mocker):
     boto_mock = mocker.patch.object(aws_ses_client, '_client', create=True)
     mocker.patch.object(aws_ses_client, 'statsd_client', create=True)
     error_response = {
@@ -104,7 +104,7 @@ def test_send_email_raises_bad_email_as_InvalidEmailError(mocker):
     boto_mock.send_email.side_effect = botocore.exceptions.ClientError(error_response, 'opname')
     mocker.patch.object(aws_ses_client, 'statsd_client', create=True)
 
-    with pytest.raises(InvalidEmailError) as excinfo:
+    with pytest.raises(EmailClientNonRetryableException) as excinfo:
         aws_ses_client.send_email(
             source=Mock(),
             to_addresses='definitely@invalid_email.com',