address review

- use `curses_set_error_*` prefix for error helpers
- remove some macros with predefined messages
- cleanly report both NULL and ERR cases

Author: picnixz

Include/py_curses.h

@@ -108,6 +108,13 @@ static void **PyCurses_API;
 static const char catchall_ERR[]  = "curses function returned ERR";
 static const char catchall_NULL[] = "curses function returned NULL";
 
+#if defined(CURSES_MODULE) || defined(CURSES_PANEL_MODULE)
+/* Error messages shared by the curses package */
+#  define CURSES_ERROR_FORMAT           "%s() returned %s"
+#  define CURSES_ERROR_VERBOSE_FORMAT   "%s() (called by %s()) returned %s"
+#  define CURSES_ERROR_MUST_CALL_FORMAT "must call %s() first"
+#endif
+
 #ifdef __cplusplus
 }
 #endif