Localize notification_utils to the API

This changeset pulls in all of the notification_utils code directly into the API and removes it as an external dependency.  We are doing this to cut down on operational maintenance of the project and will begin removing parts of it no longer needed for the API.

Signed-off-by: Carlo Costino <carlo.costino@gsa.gov>

app/errors.py

@@ -1,12 +1,12 @@
 from flask import current_app, json, jsonify
 from jsonschema import ValidationError as JsonSchemaValidationError
 from marshmallow import ValidationError
-from notifications_utils.recipients import InvalidEmailError
 from sqlalchemy.exc import DataError
 from sqlalchemy.orm.exc import NoResultFound
 
 from app.authentication.auth import AuthError
 from app.exceptions import ArchiveValidationError
+from notifications_utils.recipients import InvalidEmailError
 
 
 class VirusScanError(Exception):