I am using Powerline in my terminals and had an issue with the font. After messing with it I realize I was using a font that has not been patched for Powerline. I changed the gnome-terminal font from "Fira Mono Regular"
to "DejaVu Sans Mono Book" and it worked.

My steps on Pop! OS which is an Ubuntu 18.10 flavor.

# apt install powerline
$  rrosso  ~  tail .bashrc
# Powerline
if [ -f /usr/share/powerline/bindings/bash/powerline.sh ]; then
    source /usr/share/powerline/bindings/bash/powerline.sh
fi
```