refactored the requires_auth handler to raise exceptions

hopefully cleans up code flow and readability [a tiny bit].
raise an AuthException in auth.py, and catch it in errors.py to
save on returning error_repsonse values throughout the function

app/authentication/auth.py

@@ -5,54 +5,65 @@ from notifications_python_client.errors import TokenDecodeError, TokenExpiredErr
 from app.dao.api_key_dao import get_model_api_keys
 
 
-def authentication_response(message, code):
-    return jsonify(result='error',
-                   message={"token": [message]}
-                   ), code
+class AuthError(Exception):
+    def __init__(self, message, code):
+        self.message = {"token": [message]}
+        self.code = code
 
 
-def requires_auth():
-    auth_header = request.headers.get('Authorization', None)
+def get_auth_token(req):
+    auth_header = req.headers.get('Authorization', None)
     if not auth_header:
-        return authentication_response('Unauthorized, authentication token must be provided', 401)
+        raise AuthError('Unauthorized, authentication token must be provided', 401)
 
     auth_scheme = auth_header[:7]
 
     if auth_scheme != 'Bearer ':
-        return authentication_response('Unauthorized, authentication bearer scheme must be used', 401)
+        raise AuthError('Unauthorized, authentication bearer scheme must be used', 401)
 
-    auth_token = auth_header[7:]
+    return auth_header[7:]
+
+
+def requires_auth():
+    auth_token = get_auth_token(request)
     try:
         client = get_token_issuer(auth_token)
     except TokenDecodeError:
-        return authentication_response("Invalid token: signature", 403)
+        raise AuthError("Invalid token: signature", 403)
 
     if client == current_app.config.get('ADMIN_CLIENT_USER_NAME'):
-        errors_resp = get_decode_errors(auth_token, current_app.config.get('ADMIN_CLIENT_SECRET'), expiry_date=None)
-        return errors_resp
+        return handle_admin_key(auth_token, current_app.config.get('ADMIN_CLIENT_SECRET'))
 
-    secret_keys = get_model_api_keys(client)
-    for api_key in secret_keys:
-        errors_resp = get_decode_errors(auth_token, api_key.unsigned_secret, api_key.expiry_date)
-        if not errors_resp:
-            if api_key.expiry_date:
-                return authentication_response("Invalid token: revoked", 403)
-            else:
-                _request_ctx_stack.top.api_user = api_key
-                return
+    api_keys = get_model_api_keys(client)
 
-    if not secret_keys:
-        errors_resp = authentication_response("Invalid token: no api keys for service", 403)
-    current_app.logger.info(errors_resp)
-    return errors_resp
+    for api_key in api_keys:
+        try:
+            get_decode_errors(auth_token, api_key.unsigned_secret)
+        except TokenDecodeError:
+            continue
+
+        if api_key.expiry_date:
+            raise AuthError("Invalid token: revoked", 403)
+
+        _request_ctx_stack.top.api_user = api_key
+        return
+
+    if not api_keys:
+        raise AuthError("Invalid token: no api keys for service", 403)
+    else:
+        raise AuthError("Invalid token: signature", 403)
 
 
-def get_decode_errors(auth_token, unsigned_secret, expiry_date=None):
+def handle_admin_key(auth_token, secret):
+    try:
+        get_decode_errors(auth_token, secret)
+        return
+    except TokenDecodeError as e:
+        raise AuthError("Invalid token: signature", 403)
+
+
+def get_decode_errors(auth_token, unsigned_secret):
     try:
         decode_jwt_token(auth_token, unsigned_secret)
-    except TokenExpiredError:
-        return authentication_response("Invalid token: expired", 403)
-    except TokenDecodeError:
-        return authentication_response("Invalid token: signature", 403)
-    else:
-        return None
+    except TokenExpiredError as e:
+        raise AuthError("Invalid token: expired")

app/errors.py

@@ -5,6 +5,7 @@ from flask import (
 from sqlalchemy.exc import SQLAlchemyError, DataError
 from sqlalchemy.orm.exc import NoResultFound
 from marshmallow import ValidationError
+from app.authentication.auth import AuthError
 
 
 class InvalidRequest(Exception):
@@ -23,6 +24,10 @@ class InvalidRequest(Exception):
 
 def register_errors(blueprint):
 
+    @blueprint.app_errorhandler(AuthError)
+    def authentication_error(error):
+        return jsonify(result='error', message=error.message), error.code
+
     @blueprint.app_errorhandler(ValidationError)
     def validation_error(error):
         current_app.logger.error(error)

tests/app/authentication/test_authentication.py

@@ -171,9 +171,9 @@ def test_authentication_returns_token_expired_when_service_uses_expired_key_and_
             assert data['message'] == {"token": ['Invalid token: revoked']}
 
 
-def test_authentication_returns_error_when_api_client_has_no_secrets(notify_api,
-                                                                     notify_db,
-                                                                     notify_db_session):
+def test_authentication_returns_error_when_admin_client_has_no_secrets(notify_api,
+                                                                       notify_db,
+                                                                       notify_db_session):
     with notify_api.test_request_context():
         with notify_api.test_client() as client:
             api_secret = notify_api.config.get('ADMIN_CLIENT_SECRET')