Error(s) in re-building vignettes:
  ...
--- re-building 'introduction.Rmd.rsp' using rsp


processing file: /home/hornik/tmp/R.check/r-devel-clang/Work/PKGS/rbi.helpers.Rcheck/vign_test/rbi.helpers/vignettes/introduction.Rmd
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output file: introduction.md

Error: processing vignette 'introduction.Rmd.rsp' failed with diagnostics:
there is no package called 'markdown'
--- failed re-building 'introduction.Rmd.rsp'

SUMMARY: processing the following file failed:
  'introduction.Rmd.rsp'

Error: Vignette re-building failed.
Execution halted