Add a doctest for GLPK error handling and verbose output

[jdemeyer]

The interaction between GLPK error handling and verbose output should be doctested. This would break without the custom have_error.patch for GLPK in Sage.

CC: @kiwifb

Component: doctest coverage

Author: Jeroen Demeyer

Branch/Commit: 75e8fe2

Reviewer: Matthias Koeppe

Issue created by migration from https://trac.sagemath.org/ticket/20832

[jdemeyer]

Branch: u/jdemeyer/add_a_doctest_for_glpk_error_handling_and_verbose_output

[jdemeyer]

New commits:

49bab5b

Add a doctest for GLPK error handling and verbose output

[jdemeyer]

Commit: 49bab5b

[mkoeppe]

comment:3

Positive review, though I personally would think it would be better to test whether there is some output rather than test for specific output, which might change whenever a new version of GLPK is installed.

[mkoeppe]

Reviewer: Matthias Koeppe

[jdemeyer]

comment:4

Replying to @mkoeppe:

it would be better to test whether there is some output

How would you write the doctest then? The ellipsis ... matches the empty string, so you need to write at least some part of the verbose output in the doctest.

[mkoeppe]

comment:5

How about

      0: obj ...

[vbraun]

comment:6

sage -t --long src/sage/libs/glpk/error.pyx
**********************************************************************
File "src/sage/libs/glpk/error.pyx", line 98, in sage.libs.glpk.error.setup_glpk_error_handler
Failed example:
    p.solve()
Expected:
          0: obj =   3.000000000e+00  infeas =  3.000e+00 (0)
    *     1: obj =   2.000000000e+00  infeas =  0.000e+00 (0)
    *     2: obj =   2.400000000e+00  infeas =  0.000e+00 (0)
    +     2: mip =     not found yet <=              +inf        (1; 0)
    +     2: >>>>>   2.400000000e+00 <=   2.400000000e+00   0.0% (1; 0)
    +     2: mip =   2.400000000e+00 <=     tree is empty   0.0% (0; 1)
    2.4
Got:
          0: obj =   3.000000000e+00  infeas =  3.000e+00 (0)
    *     1: obj =   2.000000000e+00  infeas =  0.000e+00 (0)
    *     2: obj =   2.400000000e+00  infeas =  0.000e+00 (0)
    +     2: mip =     not found yet <=              +inf        (1; 0)
    +     2: >>>>>   2.400000000e+00 <=   2.400000000e+00   0.0% (1; 0)
    +     2: mip =   2.400000000e+00 <=     tree is empty   0.0% (0; 1)
    2.4000000000000004
**********************************************************************
1 item had failures:
   1 of  10 in sage.libs.glpk.error.setup_glpk_error_handler
    [11 tests, 1 failure, 1.10 s]

[sagetrac-git]

Changed commit from 49bab5b to 75e8fe2

[sagetrac-git]

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

75e8fe2

Make GLPK verbose doctest more robust

[vbraun]

Changed branch from u/jdemeyer/add_a_doctest_for_glpk_error_handling_and_verbose_output to 75e8fe2