throw error when if invalid Redis url is passed

[alias-rahil]

The current published version of code-executor doesn't throw error when trying to connect to an invalid Redis URL. Instead it connects to localhost:6379. Need to fix this.

[thebongy]

Actually, it doesn't connect to localhost:6379

it just silently fails to connect, so its impossible to know right now if the library connected to redis, or it didn't

[Seiman2004]

just use the code-execution-engine package, works better than this one