Fixed an error
Merge branch 'u/Bruce/ticket/15958' of trac.sagemath.org:sage into 15958
add doctests, improve documentation, duplicate the fix in partition_algebra.py
fix Hecke eigenvalues recurrence
dev.abandon takes a mandatory argument

The docstring claimed that ticket_or_branch=None would abandon the current
branch. This failed with an error that None is not a string. It could not work
anyway since one can not abandon the current branch.
Trac #15958: Bug in Partition Algebras

There is a bug in the implementation of the product in partition
algebras.

{{{
sage: A = PartitionAlgebra(1,17)
sage: g = SetPartitionsAk(1).list()
sage: a = A[g[1]]
sage: a
P[{{-1}, {1}}]
sage: a*a
P[{{-1}, {1}}]
}}}

This should return

{{{
17*P[{{-1}, {1}}]
}}}

URL: http://trac.sagemath.org/15958
Reported by: Bruce
Ticket author(s): Bruce Westbury
Reviewer(s): Darij Grinberg, Chwas Ahmed
Trac #16249: dev.abandon() fails

The docstring says that the default parameter `ticket_or_branch=None`
refers to the current branch. However, deleting the current branch is
not possible. Currently, the error message is not very helpful:
{{{
sage: dev.abandon()
ValueError: name must be a string
}}}
Now it prints:
{{{
sage: dev.abandon()
TypeError: abandon() takes at least 2 arguments (1 given)
}}}

URL: http://trac.sagemath.org/16249
Reported by: saraedum
Ticket author(s): Julian Rüth
Reviewer(s): Volker Braun
Trac #15201: Problem with Hecke eigenvalues with the same index as the level

It seems to be a problem to compute Hecke eigenvalues for Modular Symbol
subspaces at integers dividing the level N unless the eigenvalue for the
Hecke operator at N is computed first.
I have verified this problem for sage versions between 5.8 and
5.12.beta.

Example

{{{
sage: M=ModularSymbols(5,6,sign=1)
sage: S=M.decomposition()
sage: f=S[0]
sage: f.eigenvalue(10)
IndexError                                Traceback (most recent call
last)
...
IndexError: n must be a positive integer
sage: f.eigenvalue(5)
25
sage: f.eigenvalue(10)
50
}}}

URL: http://trac.sagemath.org/15201
Reported by: fstromberg
Ticket author(s): Alex Ghitza
Reviewer(s): Peter Bruin