Add errors.not_found_on_none helper

Also display correct info when `using hug`.

apphelpers/errors/__init__.py

@@ -1,6 +1,8 @@
 try:
-    print("apphelpers: using FastAPI")
     from apphelpers.errors.fastapi import *  # noqa: F401, F403
+
+    print("apphelpers: using FastAPI")
 except ImportError:
-    print("apphelpers: using hug")
     from apphelpers.errors.hug import *  # noqa: F401, F403
+
+    print("apphelpers: using hug")

apphelpers/errors/fastapi.py

@@ -1,8 +1,10 @@
 from dataclasses import dataclass
-from typing import ClassVar
+from typing import ClassVar, Optional, TypeVar
 
 from fastapi import HTTPException, status
 
+T = TypeVar("T")
+
 
 @dataclass
 class BaseError(HTTPException):
@@ -46,3 +48,9 @@ class HTTP409Conflict(BaseError):
 @dataclass
 class InvalidSessionError(HTTP401Unauthorized):
     detail: str = "Invalid Session"
+
+
+def not_found_on_none(obj: Optional[T], detail: str = "Not Found") -> T:
+    if obj is None:
+        raise HTTP404NotFound(detail)
+    return obj

apphelpers/errors/hug.py

@@ -1,5 +1,9 @@
+from typing import Optional, TypeVar
+
 from falcon import HTTPError, status_codes
 
+T = TypeVar("T")
+
 
 class BaseError(HTTPError):
     # Whether to report this error to honeybadger
@@ -44,3 +48,9 @@ class InvalidSessionError(BaseError):
 class ConflictError(BaseError):
     status = status_codes.HTTP_409
     description = "Duplicate resource"
+
+
+def not_found_on_none(obj: Optional[T], detail: str = "Not Found") -> T:
+    if obj is None:
+        raise NotFoundError(description=detail)
+    return obj