venv and apt-get update

ml-agents/tests/yamato/yamato_utils.py

 
     # Set up the venv and install mlagents
     if platform == "linux":
-        subprocess.check_call("sudo apt-get install -y python3-venv", shell=True)
+        subprocess.check_call(
+            "sudo apt-get update && sudo apt-get install -y python3-venv", shell=True
+        )
 
     subprocess.check_call(f"python3 -m venv {venv_path}", shell=True)
     pip_commands = ["--upgrade pip", "--upgrade setuptools"]