double negation in skip_if_not() message

[dpprdan]

The message in skip_if_not() is always appended with " is not TRUE". This makes sense for the deparse(substitute(condition)) default. It may not for custom messages.

Case in point is the googledrive package, where skip_if_not(drive_has_token(), "No Drive token") results in "No Drive token is not TRUE".

This can be easily fixed IMHO if skip_if_not() is modelled after skip_if(), i.e. if custom messages are shown as is and only the default message is "{condition} is not TRUE".

I can make a PR, if you agree.

[hadley]

Yeah, agreed, and a PR would be great 😄