CI/CLN: update travis
update and cleanup Travis 

closes #36601 

> try rebasing and we'll see if travis fixes itself

This particular Travis failure has been affecting everything all day. any idea where this is coming from? > any idea where this is coming from?

I set the number of workers to 1, and it works now. It's almost identical to what I saw on Raspberry Pi. I think the root cause is pytest-xdist. It probably has a problem specific to ARM architecture. > > any idea where this is coming from?
> 
> I set the number of workers to 1, and it works now. It's almost identical to what I saw on Raspberry Pi. I think the root cause is pytest-xdist. It probably has a problem specific to ARM architecture.

oh wow, ok! ping on green. thanks @fangchenli 