Use raw string to fix this.
Regression from d8978a8c4f
tdf#116156 tdf#157162 tdf#159528 Fix glitches in officehelper.py
Change-Id: I6f68fdc5988c05b41dc91619947d0d97d04bc739
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/174108
Reviewed-by: Julien Nabet <serval2412@yahoo.fr>
Tested-by: Jenkins