In my opinion you have three options:
If the pastebins aren't huge just embed them in the post.
Ask the OP to reupload the pastebins without expiration.
Reupload the pastebins yourself without expiration.
In the case you mention, the pastebins aren't extremely big, so they could be embedded.
Also, if you look closely, they aren't three pastebins, but ...
I agree with BeastOfCaerbannog, wholly.
The system can handle large-ish pastes and will tell you when it can't. Just remember that you don't have to indent you can use ~~~ fences before and after code and that saves you 4n characters.
But as a fourth point, if you know what you're looking at, you could edit in the just relevant error message or code fragment ...