failure value -6

[yonicd]

what does this failure mean? i have seen it a few times locally, but can't find any example online

library(leaflet)
library(htmltools)
library(webshot)

tagList(
  tags$h1( 'Leaflet Map for Screenshot' )
  ,leaflet() %>% addTiles() %>% fitBounds(0, 40, 10, 50)
) %>%
  html_print %>%
  # get forward slash on windows
  normalizePath(.,winslash="/") %>%
  # replace drive:/ with drive:// so C:/ becomes C://
  gsub(x=.,pattern = ":/",replacement="://") %>%
  # appends file:/// to make valid uri
  paste0("file://",.) %>%
  # screenshot it for lots of good reasons
  webshot( file = "stream_screen.png", delay = 3 )
#> Error in webshot(., file = "stream_screen.png", delay = 3): webshot.js returned failure value: -6

details::details(sessioninfo::session_info(),summary = 'session info')

session info

─ Session info ───────────────────────────────────────────────────────────────
 setting  value                       
 version  R version 3.6.1 (2019-07-05)
 os       macOS Mojave 10.14.5        
 system   x86_64, darwin15.6.0        
 ui       X11                         
 language (EN)                        
 collate  en_US.UTF-8                 
 ctype    en_US.UTF-8                 
 tz       America/New_York            
 date     2020-03-04                  

─ Packages ───────────────────────────────────────────────────────────────────
 package     * version    date       lib source                            
 assertthat    0.2.1      2019-03-21 [1] CRAN (R 3.6.0)                    
 backports     1.1.5      2019-10-02 [1] CRAN (R 3.6.0)                    
 callr         3.4.2      2020-02-12 [1] CRAN (R 3.6.1)                    
 cli           2.0.1      2020-01-08 [1] CRAN (R 3.6.0)                    
 clipr         0.7.0      2019-07-23 [1] CRAN (R 3.6.0)                    
 crayon        1.3.4      2017-09-16 [1] CRAN (R 3.6.0)                    
 crosstalk     1.0.0      2016-12-21 [1] CRAN (R 3.6.0)                    
 desc          1.2.0      2019-12-01 [1] Github (r-lib/desc@61205f6)       
 details       0.2.1      2020-01-12 [1] local                             
 digest        0.6.25     2020-02-23 [1] CRAN (R 3.6.0)                    
 evaluate      0.14       2019-05-28 [1] CRAN (R 3.6.0)                    
 fansi         0.4.1      2020-01-08 [1] CRAN (R 3.6.0)                    
 fastmap       1.0.1      2019-10-08 [1] CRAN (R 3.6.0)                    
 glue          1.3.1.9000 2020-02-07 [1] Github (tidyverse/glue@7131fc3)   
 highr         0.8        2019-03-20 [1] CRAN (R 3.6.0)                    
 htmltools   * 0.4.0      2019-10-04 [1] CRAN (R 3.6.0)                    
 htmlwidgets   1.5.1      2019-10-08 [1] CRAN (R 3.6.0)                    
 httpuv        1.5.2      2019-09-11 [1] CRAN (R 3.6.0)                    
 httr          1.4.1      2019-08-05 [1] CRAN (R 3.6.0)                    
 jsonlite      1.6.1      2020-02-02 [1] CRAN (R 3.6.0)                    
 knitr         1.28       2020-02-06 [1] CRAN (R 3.6.0)                    
 later         1.0.0.9002 2020-03-03 [1] Github (r-lib/later@0fb877a)      
 leaflet     * 2.0.2      2018-08-27 [1] CRAN (R 3.6.0)                    
 magrittr      1.5        2014-11-22 [1] CRAN (R 3.6.0)                    
 mime          0.9        2020-02-04 [1] CRAN (R 3.6.0)                    
 png           0.1-7      2013-12-03 [1] CRAN (R 3.6.0)                    
 processx      3.4.2      2020-02-09 [1] CRAN (R 3.6.1)                    
 promises      1.1.0.9000 2020-03-03 [1] Github (rstudio/promises@627dfc6) 
 ps            1.3.2      2020-02-13 [1] CRAN (R 3.6.1)                    
 R6            2.4.1      2019-11-12 [1] CRAN (R 3.6.0)                    
 Rcpp          1.0.3      2019-11-08 [1] CRAN (R 3.6.1)                    
 rlang         0.4.5      2020-03-01 [1] CRAN (R 3.6.0)                    
 rmarkdown     2.1.1      2020-01-30 [1] Github (rstudio/rmarkdown@18ba267)
 rprojroot     1.3-2      2018-01-03 [1] CRAN (R 3.6.0)                    
 sessioninfo   1.1.1      2018-11-05 [1] CRAN (R 3.6.0)                    
 shiny         1.4.0      2019-10-10 [1] CRAN (R 3.6.0)                    
 stringi       1.4.6      2020-02-17 [1] CRAN (R 3.6.1)                    
 stringr       1.4.0      2019-02-10 [1] CRAN (R 3.6.0)                    
 webshot     * 0.5.2      2019-11-22 [1] CRAN (R 3.6.0)                    
 withr         2.1.2      2018-03-15 [1] CRAN (R 3.6.0)                    
 xfun          0.12       2020-01-13 [1] CRAN (R 3.6.0)                    
 xml2          1.2.2      2019-08-09 [1] CRAN (R 3.6.0)                    
 xtable        1.8-4      2019-04-21 [1] CRAN (R 3.6.0)                    
 yaml          2.2.1      2020-02-01 [1] CRAN (R 3.6.0)                    

[1] /Library/Frameworks/R.framework/Versions/3.6/Resources/library

^{Created on 2020-03-04 by the reprex package (v0.3.0)}