REPL: (y-or-n-p) outputs retry prompt twice for one invalid input

[proehlen]

Thanks for this extension. This is maybe a low priority issue but I thought I'd log it in case it's a symptom of something worth fixing:

The standard function (y-or-n-p) outputs any retry prompt twice for any single non-valid input. In the below example, I only entered the letter 'a' once in response to the first prompt:

(y-or-n-p)
(y or n)                                                       <--- I entered "a" here
Please type "y" for yes or "n" for no.
(y or n) 
Please type "y" for yes or "n" for no.
(y or n) 

In the SBCL REPL, I only get the retry prompt once as expected.