Error in re-building vignettes:
  ...
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.
Loading required package: Rcpp
rstanarm (Version 2.17.4, packaged: 2018-04-13 01:51:52 UTC)
- Do not expect the default priors to remain the same in future rstanarm versions.
Thus, R scripts should specify priors explicitly, even if they are just the defaults.
- For execution on a local, multicore CPU with excess RAM we recommend calling
options(mc.cores = parallel::detectCores())
- Plotting theme set to bayesplot::theme_default().
NOTE: As of emmeans versions > 1.2.3,
      The 'cld' function will be deprecated in favor of 'CLD'.
      You may use 'cld' only if you have package:multcomp attached.

Attaching package: 'dplyr'

The following objects are masked from 'package:stats':

    filter, lag

The following objects are masked from 'package:base':

    intersect, setdiff, setequal, union

Warning in ypredloo - y :
  longer object length is not a multiple of shorter object length
Warning: There were 9 divergent transitions after warmup. Increasing adapt_delta above 0.95 may help. See
http://mc-stan.org/misc/warnings.html#divergent-transitions-after-warmup
Warning: Examine the pairs() plot to diagnose sampling problems

Warning: Markov chains did not converge! Do not analyze results!
Warning: There were 13 divergent transitions after warmup. Increasing adapt_delta above 0.95 may help. See
http://mc-stan.org/misc/warnings.html#divergent-transitions-after-warmup
Warning: Examine the pairs() plot to diagnose sampling problems

Warning: Markov chains did not converge! Do not analyze results!

Attaching package: 'plotly'

The following object is masked from 'package:ggplot2':

    last_plot

The following object is masked from 'package:stats':

    filter

The following object is masked from 'package:graphics':

    layout

Quitting from lines 512-540 (bayesian.Rmd) 
Error: processing vignette 'bayesian.Rmd' failed with diagnostics:
there is no package called 'webshot'
Execution halted