I will close this "error report thread" here, since I got a perfect answer at https://ask.sagemath.org/question/40935/bug-report-kernel-dies-after-1-hour-while-dividing-polynomials/
The workaround is not to create the quotient ring. It is better to work in polynomial rings and to use the "lift" command directly in Sage. Thank you. -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-support+unsubscr...@googlegroups.com. To post to this group, send email to sage-support@googlegroups.com. Visit this group at https://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout.
