Graph plotting: edge colors

[jm58660]

This simple patch allows using edge_color as a default color together with edge_colors. To test try

g = graphs.PetersenGraph()
g.show(edge_color='red', edge_colors={'blue': [(1,2), (6,8)], 'green': [(5,8)]})

This is a part of #13827.

CC: @paulmasson

Component: graph theory

Author: Jori Mäntysalo

Branch/Commit: 4b57914

Reviewer: Paul Masson

Issue created by migration from https://trac.sagemath.org/ticket/21053

[jm58660]

Branch: u/jmantysalo/graph-edge-colors

[jm58660]

Commit: ac618a6

[jm58660]

comment:2

This was also an easy one.

Font sizes will be harder...

---

New commits:

ac618a6

Allow using edge_color and edge_colors together.

[paulmasson]

comment:3

Doctests pass. Documentation builds. Example runs as expected.

One minor change: make these two lines

+                    'edge_color': 'The default color for edges not listed in '
+                    'edge_colors.',

into one

+                    'edge_color': 'The default color for edges not listed in edge_colors.',

for legibility, then you can set positive review from me.

[paulmasson]

Reviewer: Paul Masson

[sagetrac-git]

Changed commit from ac618a6 to 4b57914

[sagetrac-git]

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

4b57914

Reviewer's comment.

[jm58660]

comment:5

Replying to @paulmasson:

... for legibility, then you can set positive review from me.

Done.