pyqt6: Fix QPrinter::pageSize no longer present in pyqt6

src/calibre/gui2/widgets.py

@@ -10,7 +10,7 @@ from qt.core import (QIcon, QFont, QLabel, QListWidget, QAction, QEvent,
         QCursor, QColor, QWidget, QPixmap, QSplitterHandle, QToolButton,
         Qt, pyqtSignal, QSize, QSplitter, QPainter, QPageSize, QPrinter,
         QLineEdit, QComboBox, QPen, QGraphicsScene, QMenu, QStringListModel, QKeySequence,
-        QCompleter, QTimer, QRect, QGraphicsView, QPagedPaintDevice, QPalette, QClipboard)
+        QCompleter, QTimer, QRect, QGraphicsView, QPalette, QClipboard)
 
 from calibre.constants import iswindows, ismacos
 from calibre.gui2 import (error_dialog, pixmap_to_data, gprefs,
@@ -1275,7 +1275,7 @@ class PaperSizes(QComboBox):  # {{{
             if iswindows or ismacos:
                 # On Linux, this can cause Qt to load the system cups plugin
                 # which can crash: https://bugs.launchpad.net/calibre/+bug/1861741
-                PaperSizes.system_default_paper_size = 'letter' if QPrinter().pageSize() == QPagedPaintDevice.PageSize.Letter else 'a4'
+                PaperSizes.system_default_paper_size = 'letter' if QPrinter().pageLayout().pageSize().id() == QPageSize.PageSizeId.Letter else 'a4'
         if not choices:
             from calibre.ebooks.conversion.plugins.pdf_output import PAPER_SIZES
             choices = PAPER_SIZES