Runtime error on Scribus CMYK PDF export
#### Summary:
On exporting to Scribus CMYK PDF I got this Python error:
```
Traceback (most recent call last):
File "scribus_export_pdf.py", line 152, in <module>
Scribus().run()
File "/tmp/.mount_InkscadfDxc9/usr/share/inkscape/extensions/inkex/base.py", line 140, in run
self.save_raw(self.effect())
File "/tmp/.mount_InkscadfDxc9/usr/share/inkscape/extensions/inkex/base.py", line 165, in save_raw
self.save(self.options.output)
File "scribus_export_pdf.py", line 147, in save
call(SCRIBUS_EXE, '-g', '-py', py_file, svg_file, pdf_file)
File "/tmp/.mount_InkscadfDxc9/usr/share/inkscape/extensions/inkex/command.py", line 182, in call
return _call(program, *args, **kwargs)
File "/tmp/.mount_InkscadfDxc9/usr/share/inkscape/extensions/inkex/command.py", line 171, in _call
raise ProgramRunError("Return Code: {}: {}\n{}\nargs: {}".format(
inkex.command.ProgramRunError: Return Code: 1: b'Gtk-Message: 20:37:30.710: Failed to load module "canberra-gtk-module"\nGtk-Message: 20:37:30.711: Failed to load module "canberra-gtk-module"\nImportError: No module named site\n'
b''
args: ['/usr/bin/scribus', '-g', '-py', '/tmp/inktmpmty4_aqv/scribus.py', '/tmp/inktmpmty4_aqv/in.svg', '/tmp/inktmpmty4_aqv/out.pdf']
```
#### Steps to reproduce:
- Install Scribus.
- Download Inkscpape 1.0.1 appImage and start it.
- Create a new document. Follow [steps](https://wiki.inkscape.org/wiki/index.php/Release_notes/1.0.1#Color-managed_PDF_export_using_Scribus) decribed in wiki.
- Export to Scribus CMYK PDF
#### What happened?
- Above error occurred.
#### What should have happened?
- Exporting should be work.
#### Version Info:
```
- Inkscape Version: 1.0.1 (3bc2e81, 2020-09-07) official appImage(!)
- Scribus version: 1.5.5 (31. July 2019, Build ID: C--T-F-C1.16.0-64bit, 9.50 Ghostscript) /usr/bin/scribus
- Operating System: Ubuntu
- Operating System version: 20.04
```
issue