Hi Bojan,
Based on those strings, it's a bit hard to determine -- the typical method to get more information is to search through all files for the message you get, e.g.
(venv)valhallasw@lisilwen:~/src/pwb/pywikibot-core$ grep -R * -i -e 'disambiguationspage does not exist'
but this returns nothing for your errors. Could you copy-paste some more context (in windows, right-click on the icon in the top-left corner, edit, mark; then select the area with your mouse, then right-click on the icon in the top-left corner, edit, copy), or check the verbose output, as Amir suggested?
Merlijn