Prior this commit, the error message is too cryptic. This commit fixes
that by specifying in the message, the actual argument it got during
precondition.
I'm going to close this because I think gulp upgrade messages should actually exist in gulp itself, not the undertaker library, which was created for v4 exclusively.
When updating from gulp 3 to 4, this function is the first one to fail when the file contains the old exec chain:
Prior this commit, the error message is too cryptic. This commit fixes that by specifying in the message, the actual argument it got during precondition.