fix(speedtest): added a error message for if speedtest is not installed

speedtest/speedtest.py

@@ -36,11 +36,14 @@ class Speedtest(commands.Cog):
         return "\n".join(text)
 
     async def run_speedtest(self) -> str | Any:
+        try:
             process = await asyncio.create_subprocess_exec(
                 "speedtest", "-f json", "--accept-license",
                 stdout=subprocess.PIPE,
                 stderr=subprocess.PIPE
             )
+        except FileNotFoundError:
+            return "Speedtest CLI is not installed."
         stdout, stderr = await process.communicate()
         if process.returncode != 0:
             return stderr.decode("utf-8")