Failed to XInitThreads()

[Comm Sp]

Hi

         I have installed Ubuntu 18.04 and GNU Radio 3.8 on two different computers several times using these commands from https://wiki.gnuradio.org/index.php/InstallingGR#Ubuntu_PPA_Installation.

sudo add-apt-repository ppa:gnuradio/gnuradio-releases, (or 
sudo add-apt-repository ppa:gnuradio/gnuradio-master)then

sudo apt-get update

sudo apt install gnuradio

But each time my flowgraph runs with the following warning:

<<< Welcome to GNU Radio Companion 3.8.1.0 >>>

Block paths:
/usr/share/gnuradio/grc/blocks

Loading: "/home/mgusr/Flowgraphs/Test.grc"
>>> Done

Generating: '/home/mgusr/Flowgraphs/Test.py'

Executing: /usr/bin/python3 -u /home/mgusr/Flowgraphs/Test.py

Warning: failed to XInitThreads()

>>> Done

My flowgraph runs but I have seen some effects that shouldn't appear (e.g., FFT of a cosine doesn't have two simple impulses) and perhaps GUI not updating properly. How can I fix this problem?

Thanks.