Fix invalid sprintf

[howardjohn]

We are using %s but the input is not a string. This can result in bad error messages, for example https://go.dev/play/p/NoimdDgOdDR

[evanphx]

This is using %v so that the output contains quotes, as that's how fmt handles string inputs.

[howardjohn]

I posted a link to a go playground example

tl;dr, for a non-string input like 10

before: %!s(int=10)
after: 10

[evanphx]

Oh I'm sorry, I misread this entirely.