bg_color parameter doesn't work in version 2.30

If graph_draw is called with a bg_color parameter, the following warning is printed and the background color remains transparent:

/usr/lib/python3/dist-packages/graph_tool/draw/cairo_draw.py:640: UserWarning: Unknown parameter: bg_color
  warnings.warn("Unknown parameter: " + k, UserWarning)

This used to work in graph-tool 2.29. A regression test said:

c4c7e6750a29b874dcb5f8476558dd0d16a513f7 is the first bad commit
commit c4c7e6750a29b874dcb5f8476558dd0d16a513f7
Author: Tiago de Paula Peixoto <tiago@skewed.de>
Date:   Sun Mar 22 11:56:53 2020 +0000

    graph_draw(): revamp fit_view and matplotlib support
    
    This fixes issues #628, #516, #461, #418, #280.

:040000 040000 06ebdee6068ca7cd55b7e9dd7ab99c8cd6a97ddb 16586513b513644af657dc426507316fc3260d7d M      src

I'm betting that the relevant change in that commit is:

-
-        if "bg_color" in kwargs:
-            bg_color = kwargs["bg_color"]
-            del  kwargs["bg_color"]
-            cr.set_source_rgba(bg_color[0], bg_color[1],
-                               bg_color[2], bg_color[3])
-            cr.paint()