hugolib: Improve shortcode error message
hugolib: Improve shortcode error message

fedelibre/hugo,anthonyfok/hugo,fedelibre/hugo,gohugoio/hugo,mitchchn/hugo,mdhender/hugo,digitalcraftsman/hugo,fedelibre/hugo,gohugoio/hugo,anthonyfok/hugo,fedelibre/hugo,mitchchn/hugo,digitalcraftsman/hugo,gohugoio/hugo,mdhender/hugo,anthonyfok/hugo,mdhender/hugo,mdhender/hugo