Raise a better error when contexts are pickled.

Author: HexDecimal

CHANGELOG.rst

@@ -8,13 +8,17 @@ v2.0.0
 
 Unreleased
 ------------------
+Added
  - Added some keyboard functions:
    - `tcod.event.get_keyboard_state`
    - `tcod.event.get_modifier_state`
    - `tcod.event.key_from_scancode`
    - `tcod.event.scancode_from_key`
    - `tcod.event.get_key_name`
 
+Fixed
+ - Contexts now give a more useful error when pickled.
+
 12.2.0 - 2021-04-09
 -------------------
 Added

tcod/context.py

@@ -48,10 +48,11 @@
 .. versionadded:: 11.12
 """  # noqa: E501
 import os
+import pickle
 import sys
 from typing import Any, Iterable, List, Optional, Tuple
 
-from typing_extensions import Literal
+from typing_extensions import Literal, NoReturn
 
 import tcod
 import tcod.event
@@ -366,6 +367,12 @@ def toggle_fullscreen(context: tcod.context.Context) -> None:
         '''  # noqa: E501
         return lib.TCOD_context_get_sdl_window(self._context_p)
 
+    def __reduce__(self) -> NoReturn:
+        """Contexts can not be pickled, so this class will raise
+        :class:`pickle.PicklingError`.
+        """
+        raise pickle.PicklingError("Python-tcod contexts can not be pickled.")
+
 
 @ffi.def_extern()  # type: ignore
 def _pycall_cli_output(catch_reference: Any, output: Any) -> None: