In Emacs, what does this error mean? “Warning: cl package required at runtime”

Question

I am byte-compiling a module. It gives me this warning:

 Warning: cl package required at runtime

Why is this a warning? I am well aware that I

Answer 1

I wasn't able to suppress this message after reading the comments before mine.

However, I received the following instruction from a kind person on the GNU emacs mailing list:

Require cl-lib, and then change the call to use cl-remove-if-not, instead of remove-if-not.

Which proved to be the remedy.

In sum: by 'requiring cl-lib, one must also change the name of the function/macro call.

HTH....