covering_design.py & design_catalog.py: Fix AttributeError

[vinklein]

1. Fix the following bug.

sage: C = designs.best_known_covering_design_from_LJCR(7, 3, 2)
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-1-a3d9f9e592f1> in <module>()
----> 1 C = designs.best_known_covering_design_from_LJCR(Integer(7), Integer(3), Integer(2))

/home/slabbe/GitBox/sage/local/lib/python2.7/site-packages/sage/combinat/designs/covering_design.pyc in best_known_covering_design_www(v, k, t, verbose)
    525     if verbose:
    526         print("Looking up the bounds at %s" % url)
--> 527     with urlopen(url) as f:
    528         s = bytes_to_str(f.read())
    529     if 'covering not in database' in s:  # not found

AttributeError: addinfourl instance has no attribute '__exit__'

Found by Sebastien Labbé see #26592

The root cause is that the object returned by urlopen doesn't have an __exit__ method in python2 and therefore it can not be used with a with ... as ... syntax.

2. Fix a doctest error in design_catalog.py:

sage -t --long src/sage/combinat/designs/design_catalog.py
**********************************************************************
File "src/sage/combinat/designs/design_catalog.py", line 23, in sage.combinat.designs.design_catalog
Failed example:
    C                            # optional - internet
Expected:
    (7,3,2)-covering design of size 7
    Lower bound: 7
    Method: lex covering
    Submitted on: 1996-12-01 00:00:00
Got:
    (7, 3, 2)-covering design of size 7
    Lower bound: 7
    Method: lex covering
    Submitted on: 1996-12-01 00:00:00
**********************************************************************

CC: @seblabbe @slel

Component: combinatorial designs

Keywords: thursdaysbdx

Author: Vincent Klein

Branch/Commit: 138870c

Reviewer: Sébastien Labbé

Issue created by migration from https://trac.sagemath.org/ticket/27821

[seblabbe]

comment:4

Is this a solution:

from six.moves.urllib.request import urlopen

? This is what I used in #25535.

[vinklein]

Branch: u/vklein/27821

[vinklein]

comment:6

Replying to @seblabbe:

Is this a solution:

from six.moves.urllib.request import urlopen

? This is what I used in #25535.

No because it is already used in covering_design.py.
In #25535 you use with ... as with a file objet, this works nicely.

---

New commits:

1e93e49

Trac #27821: Fix AttributeError in ...

[vinklein]

Commit: 1e93e49

[seblabbe]

comment:8

As mentionned here, two files were having the same issue. We are almost there.

There is still one small issue:

$ sage -tp --long --optional=sage,optional,external src/sage/combinat/designs/covering_design.py  src/sage/combinat/designs/design_catalog.py

gives

too many failed tests, not using stored timings
Running doctests with ID 2019-05-13-17-17-32-23591643.
Git branch: 27821
Using --optional=4ti2,bliss,cbc,ccache,cmake,cryptominisat,dot2tex,e_antic,external,glucose,latte_int,lidia,lrslib,memlimit,mpir,ninja_build,normaliz,notedown,pandoc_attributes,pycosat,pynormaliz,python2,qhull,rst2ipynb,sage,topcom
External software to be detected: cplex,ffmpeg,graphviz,gurobi,imagemagick,internet,latex,macaulay2,magma,maple,mathematica,matlab,octave,pandoc,scilab
Doctesting 2 files using 8 threads.
sage -t --long src/sage/combinat/designs/design_catalog.py
**********************************************************************
File "src/sage/combinat/designs/design_catalog.py", line 23, in sage.combinat.designs.design_catalog
Failed example:
    C                            # optional - internet
Expected:
    (7,3,2)-covering design of size 7
    Lower bound: 7
    Method: lex covering
    Submitted on: 1996-12-01 00:00:00
Got:
    (7, 3, 2)-covering design of size 7
    Lower bound: 7
    Method: lex covering
    Submitted on: 1996-12-01 00:00:00
**********************************************************************
1 item had failures:
   1 of   5 in sage.combinat.designs.design_catalog
    [4 tests, 1 failure, 0.73 s]
sage -t --long src/sage/combinat/designs/covering_design.py
    [49 tests, 0.73 s]
----------------------------------------------------------------------
sage -t --long src/sage/combinat/designs/design_catalog.py  # 1 doctest failed
----------------------------------------------------------------------
Total time for all tests: 0.8 seconds
    cpu time: 0.1 seconds
    cumulative wall time: 1.5 seconds
External software detected for doctesting: internet

[sagetrac-git]

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

138870c

Trac #27821: Fix a doctest in design_catalog.py

[sagetrac-git]

Changed commit from 1e93e49 to 138870c

[vinklein]

comment:11

The other doctest bug of design_catalog.py has been fixed.

[seblabbe]

comment:12

It works! Thank you.

[seblabbe]

Changed keywords from none to thursdaysbdx

[seblabbe]

Reviewer: Sébastien Labbé

[vbraun]

Changed branch from u/vklein/27821 to 138870c