ci: Add libsox

Author: adinhodovic

.github/workflows/run-tests.yml

@@ -29,6 +29,7 @@ jobs:
       run: |
         sudo apt-get update
         sudo apt-get install sox
+        sudo apt-get install libsox-fmt-mp3
         python -m pip install --upgrade pip
         python -m pip install flake8 pytest pytest-cov
         python -m pip install coveralls