Allow for randomness in permgroup.py test

[jdemeyer]

The following test from sage/groups/perm_gps/permgroup.py (introduced by #10334) sometimes gives different output, see #11427:

sage: G = PermutationGroup([(1,2,3), (2,3)]) 
sage: H = PermutationGroup([(1,2,4), (1,4)]) 
sage: G.isomorphism_to(H)
Permutation group morphism: 
  From: Permutation Group with generators [(2,3), (1,2,3)] 
  To:   Permutation Group with generators [(1,2,4), (1,4)] 
  Defn: [(2,3), (1,2,3)] -> [(2,4), (1,2,4)] 

In this ticket, I simply allow random output for the right hand side of Defn:.

[mhansen]

Why does it include the doctest twice? I think the following would be better:

sage: G = PermutationGroup([(1,2,3), (2,3)]) 
sage: H = PermutationGroup([(1,2,4), (1,4)]) 
sage: phi = G.isomorphism_to(H); phi
Permutation group morphism: 
  From: Permutation Group with generators [(2,3), (1,2,3)] 
  To:   Permutation Group with generators [(1,2,4), (1,4)] 
  Defn: [(2,3), (1,2,3)] -> [...] 
sage: phi(G).is_isomorphic(H)
True

[fbissey]

Indeed we have a first test marked random followed by the same test with less randomness. I would be OK with just the second test as well since only the part in "..." varies depending on what's installed.

[jdemeyer]

My idea was to keep the first test as documentation and have the second one truly as test. New version, changed "random" to "not tested, see below". Please review.

[fbissey]

I am quite happy with that explanation. I can give a positive review for that trivial patch. Which means that we will be able to close #11427 once this goes in.

[was]

I also tested that with the optional spkg installed the doctest now works.

wstein@sage:/scratch/wstein/sd32/sage-4.7.2.alpha2$ ./sage -t -long -force_lib "devel/sage/sage/groups/perm_gps/permgroup.py"
sage -t -long -force_lib "devel/sage/sage/groups/perm_gps/permgroup.py"
         [15.0 s]
 
----------------------------------------------------------------------
All tests passed!
Total time for all tests: 15.1 seconds

[was]

Above comment was meant for #11427. Sorry.