with Sage 5.7 I get:

sage: a, q, k = var('a, q, k'); assume(q > 1)                            
sage: try:
....:     sum(a*q^k, k, 0, infinity)
....: except ValueError:
....:     0
....:     
#0: simplify_sum(expr='sum(q^k,k,0,inf))
#1: simplify_sum(expr=a*'sum(q^k,k,0,inf))
0

Why do I get the #0 and #1 lines?

Paul

PS: this is one of the examples of our book (in french) about Sage at
http://sagebook.gforge.inria.fr/, and it makes our doctests fail.

Component: interfaces

Author: Nils Bruin

Branch/Commit: e5a96a1

Reviewer: Karl-Dieter Crisman, Paul Zimmermann

Issue created by migration from https://trac.sagemath.org/ticket/14308