Error(s) in re-building vignettes:
  ...
--- re-building ‘a_1_getting_started.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) and/or pandoc-citeproc not available. Falling back to R Markdown v1.
Quitting from lines 5-183 (./toc/vignettetoc.Rmd) 
Quitting from lines 5-183 (./toc/vignettetoc.Rmd) 
Error: processing vignette 'a_1_getting_started.Rmd' failed with diagnostics:
argument is of length zero
--- failed re-building ‘a_1_getting_started.Rmd’

--- re-building ‘a_2_mlrCPO_core.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) and/or pandoc-citeproc not available. Falling back to R Markdown v1.
Quitting from lines 5-183 (./toc/vignettetoc.Rmd) 
Quitting from lines 5-183 (./toc/vignettetoc.Rmd) 
Error: processing vignette 'a_2_mlrCPO_core.Rmd' failed with diagnostics:
argument is of length zero
--- failed re-building ‘a_2_mlrCPO_core.Rmd’

--- re-building ‘a_3_all_CPOs.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) and/or pandoc-citeproc not available. Falling back to R Markdown v1.
Quitting from lines 5-183 (./toc/vignettetoc.Rmd) 
Quitting from lines 5-183 (./toc/vignettetoc.Rmd) 
Error: processing vignette 'a_3_all_CPOs.Rmd' failed with diagnostics:
argument is of length zero
--- failed re-building ‘a_3_all_CPOs.Rmd’

--- re-building ‘a_4_custom_CPOs.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) and/or pandoc-citeproc not available. Falling back to R Markdown v1.
Quitting from lines 5-183 (./toc/vignettetoc.Rmd) 
Quitting from lines 5-183 (./toc/vignettetoc.Rmd) 
Error: processing vignette 'a_4_custom_CPOs.Rmd' failed with diagnostics:
argument is of length zero
--- failed re-building ‘a_4_custom_CPOs.Rmd’

--- re-building ‘z_1_getting_started_terse.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) and/or pandoc-citeproc not available. Falling back to R Markdown v1.
Quitting from lines 5-183 (./toc/vignettetoc.Rmd) 
Error: processing vignette 'z_1_getting_started_terse.Rmd' failed with diagnostics:
argument is of length zero
--- failed re-building ‘z_1_getting_started_terse.Rmd’

--- re-building ‘z_2_mlrCPO_core_terse.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) and/or pandoc-citeproc not available. Falling back to R Markdown v1.
Quitting from lines 5-183 (./toc/vignettetoc.Rmd) 
Error: processing vignette 'z_2_mlrCPO_core_terse.Rmd' failed with diagnostics:
argument is of length zero
--- failed re-building ‘z_2_mlrCPO_core_terse.Rmd’

--- re-building ‘z_3_all_CPOs_terse.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) and/or pandoc-citeproc not available. Falling back to R Markdown v1.
Quitting from lines 5-183 (./toc/vignettetoc.Rmd) 
Error: processing vignette 'z_3_all_CPOs_terse.Rmd' failed with diagnostics:
argument is of length zero
--- failed re-building ‘z_3_all_CPOs_terse.Rmd’

--- re-building ‘z_4_custom_CPOs_terse.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) and/or pandoc-citeproc not available. Falling back to R Markdown v1.
Quitting from lines 5-183 (./toc/vignettetoc.Rmd) 
Error: processing vignette 'z_4_custom_CPOs_terse.Rmd' failed with diagnostics:
argument is of length zero
--- failed re-building ‘z_4_custom_CPOs_terse.Rmd’

SUMMARY: processing the following files failed:
  ‘a_1_getting_started.Rmd’ ‘a_2_mlrCPO_core.Rmd’ ‘a_3_all_CPOs.Rmd’
  ‘a_4_custom_CPOs.Rmd’ ‘z_1_getting_started_terse.Rmd’
  ‘z_2_mlrCPO_core_terse.Rmd’ ‘z_3_all_CPOs_terse.Rmd’
  ‘z_4_custom_CPOs_terse.Rmd’

Error: Vignette re-building failed.
Execution halted