py3: fix doctests in digraph_generators.py

[dcoudert]

• fix method tournaments_nauty using to bytes_to_str
• fix doctest in method RandomDirectedGNC by avoiding to print the list of edges and testing that the digraph is acyclic instead
• fix method RandomDirectedGNR that was calling networkx.random_gnc instead of networkx.random_gnr... and then fix the doctests by avoiding to print the list of edges and testing instead that the digraph is acyclic and is a tree

CC: @tscrim @fchapoton

Component: graph theory

Author: David Coudert

Branch/Commit: 2c066f6

Reviewer: Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/26871

[dcoudert]

Branch: public/26871_digraph_generators

[dcoudert]

Commit: 2c066f6

[dcoudert]

New commits:

2c066f6

trac #26871: fix digraph generators

[tscrim]

comment:2

LGTM.

[tscrim]

Reviewer: Travis Scrimshaw

[vbraun]

Changed branch from public/26871_digraph_generators to 2c066f6

[embray]

comment:4

This tickets were closed as fixed after the Sage 8.5 release.