CVXOPTBackend: Set initial problem_name

[mkoeppe]

CVXOPTBackend forgets to set its initial problem_name, and as a result the MixedIntegerLinearProgram cannot print itself.

sage: p = MixedIntegerLinearProgram(solver="CVXOPT")
sage: p
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
...
TypeError: cannot concatenate 'str' and 'NoneType' objects
<repr(<sage.numerical.mip.MixedIntegerLinearProgram at 0x190970a70>) failed: TypeError: cannot concatenate 'str' and 'NoneType' objects>

CC: @dimpase @ingolfured @videlec @jdemeyer

Component: numerical

Author: Matthias Koeppe

Branch/Commit: f1af4ec

Reviewer: Dima Pasechnik

Issue created by migration from https://trac.sagemath.org/ticket/20332

[mkoeppe]

Branch: u/mkoeppe/cvxoptbackend__set_initial_problem_name

[mkoeppe]

Commit: eb4649c

[mkoeppe]

New commits:

eb4649c

CVXOPTBackend: Set initial problem_name

[mkoeppe]

comment:3

... needs review ...

[dimpase]

comment:4

Can we have a doctest showing that this fixes the error in the ticket description?

[sagetrac-git]

Changed commit from eb4649c to f1af4ec

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

f1af4ec

CVXOPTBackend: Add test for #20232

[dimpase]

Reviewer: Dima Pasechnik

[dimpase]

comment:6

ok, good to go.

[mkoeppe]

comment:7

Thanks for reviewing, Dima!

[mkoeppe]

Author: Matthias Koeppe

[vbraun]

Changed branch from u/mkoeppe/cvxoptbackend__set_initial_problem_name to f1af4ec