Error(s) in re-building vignettes:
--- re-building ‘converting.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) not available. Falling back to R Markdown v1.
Quitting from lines 116-129 (converting.Rmd) 
Error: processing vignette 'converting.Rmd' failed with diagnostics:
package or namespace load failed for 'ggplot2' in loadNamespace(j <- i[[1L]], c(lib.loc, .libPaths()), versionCheck = vI[[j]]):
 there is no package called 'utf8'
--- failed re-building ‘converting.Rmd’

--- re-building ‘cpp11.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) not available. Falling back to R Markdown v1.
Warning in get_engine(options$engine) :
  Unknown language engine 'cpp11' (must be registered via knit_engines$set()).
Warning in get_engine(options$engine) :
  Unknown language engine 'cpp11' (must be registered via knit_engines$set()).
Warning in get_engine(options$engine) :
  Unknown language engine 'cpp11' (must be registered via knit_engines$set()).
Warning in get_engine(options$engine) :
  Unknown language engine 'cpp11' (must be registered via knit_engines$set()).
Warning in get_engine(options$engine) :
  Unknown language engine 'cpp11' (must be registered via knit_engines$set()).
Warning in get_engine(options$engine) :
  Unknown language engine 'cpp11' (must be registered via knit_engines$set()).
Warning in get_engine(options$engine) :
  Unknown language engine 'cpp11' (must be registered via knit_engines$set()).
Warning in get_engine(options$engine) :
  Unknown language engine 'cpp11' (must be registered via knit_engines$set()).
Warning in get_engine(options$engine) :
  Unknown language engine 'cpp11' (must be registered via knit_engines$set()).
Warning in get_engine(options$engine) :
  Unknown language engine 'cpp11' (must be registered via knit_engines$set()).
Warning in get_engine(options$engine) :
  Unknown language engine 'cpp11' (must be registered via knit_engines$set()).
Warning in get_engine(options$engine) :
  Unknown language engine 'cpp11' (must be registered via knit_engines$set()).
Warning in get_engine(options$engine) :
  Unknown language engine 'cpp11' (must be registered via knit_engines$set()).
Warning in get_engine(options$engine) :
  Unknown language engine 'cpp11' (must be registered via knit_engines$set()).
Warning in get_engine(options$engine) :
  Unknown language engine 'cpp11' (must be registered via knit_engines$set()).
Warning in get_engine(options$engine) :
  Unknown language engine 'cpp11' (must be registered via knit_engines$set()).
--- finished re-building ‘cpp11.Rmd’

--- re-building ‘internals.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) not available. Falling back to R Markdown v1.
--- finished re-building ‘internals.Rmd’

--- re-building ‘motivations.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) not available. Falling back to R Markdown v1.
--- finished re-building ‘motivations.Rmd’

SUMMARY: processing the following file failed:
  ‘converting.Rmd’

Error: Vignette re-building failed.
Execution halted