[PeterT]

I think the standard approach has been to initially use a try / except block to initially attempt to import the new module name and if that fails import the old name.

See

try:
    from PyQt5.Qt import QUrl, pyqtSignal, QTimer
    from PyQt5.Qt import (QMenu, QModelIndex, QFileDialog, QIcon)
except ImportError:
    from PyQt4.Qt import QUrl, pyqtSignal, QTimer
    from PyQt4.Qt import (QMenu, QModelIndex, QFileDialog, QIcon)

as an example. (Code from the current Kobo Utilities plugin.)

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