Comment 11 for bug 1662531

With trunk on Ubuntu, the original version of 'Pre-Process File Save As...' failed (spawned inkscape process crashes) with a file which contained a group with a rect and circle, and two clones of that group, one on an additional layer. If all clones are unlinked first, everything ungrouped and moved to a single layer, the extension works as expected. There was no error message returned to the main inkscape process, only the dialog from the second instance notifying about the crash:

«Inkscape encountered an internal error and will close now.
Automatic backups of unsaved documents were done to the following locations:
        /tmp/ink_ext_XXXXXX-prepare.svg.2017_02_10_20_24_44.0.svg»

Attempting to run the same command as the extension script in the terminal directly produced also a crash (backtrace attached), so it is not related to how the second instance is spawned via Popen:

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7573d46 in SPLPEItem::removeAllPathEffects(bool) () from /home/su-v/local/src/inkscape/build/lib/libinkscape_base.so