graph-tool example failure

Hi,

I tried to following:

$ docker run -it -u user -w /home/user tiagopeixoto/graph-tool ipython
Python 3.6.5 (default, May 11 2018, 04:00:52)
Type 'copyright', 'credits' or 'license' for more information
IPython 6.3.1 -- An enhanced Interactive Python. Type '?' for help.

In [1]: from graph_tool.all import *
Unable to init server: Could not connect: Connection refused
Unable to init server: Could not connect: Connection refused
In [2]: g = Graph()
In [3]: v1 = g.add_vertex()
In [4]: v2 = g.add_vertex()
In [5]: e = g.add_edge(v1, v2)
In [6]: graph_draw(g, vertex_text=g.vertex_index, vertex_font_size=18,
   ...: output_size=(200, 200), output="two-nodes.png")
Out[6]: <PropertyMap object with key type 'Vertex' and value type 'vector<double>', for Graph 0x7f60e1fbadd8, at 0x7f60e1fbcd68>

Do I make any obvious mistake?

thanks,
mwarning

I don't see any problems. The "Unable to init server" are only warnings,
meaning that a connection with the X server could not have been established.
This can be safely ignored.

Thanks for the clarification.
I thought of <PropertyMap object ... as an error.

The png was written, but I did not see that because it was inside the docker container.