Log Message:
py-pikepdf: updated to 9.4.2

v9.4.2

- Internal type assertion error messages from qpdf that previously triggered
  a RuntimeError will now raise a PdfError. Generally these errors only occur
  in corrupted files.
- When we are updating XMP in the processing of saving, errors from updating
  XML are wrapped differently to clarify the context in which the error
  occurs.