If possible error proof .Rmd files against CRAN could not fetch https://i.creativecommons.org/l/by/4.0/80x15.png errors?

[joethorley]

Error(s) in re-building vignettes:
--- re-building ‘distributions.Rmd’ using rmarkdown
--- finished re-building ‘distributions.Rmd’

--- re-building ‘exposure-plots.Rmd’ using rmarkdown
--- finished re-building ‘exposure-plots.Rmd’

--- re-building ‘faqs.Rmd’ using rmarkdown
--- finished re-building ‘faqs.Rmd’

--- re-building ‘small-sample-bias-ref.Rmd’ using rmarkdown
--- finished re-building ‘small-sample-bias-ref.Rmd’

--- re-building ‘ssdtools.Rmd’ using rmarkdown
Could not fetch https://i.creativecommons.org/l/by/4.0/80x15.png
HttpExceptionRequest Request {
  host                 = "i.creativecommons.org"
  port                 = 443
  secure               = True
  requestHeaders       = []
  path                 = "/l/by/4.0/80x15.png"
  queryString          = ""
  method               = "GET"
  proxy                = Nothing
  rawBody              = False
  redirectCount        = 10
  responseTimeout      = ResponseTimeoutDefault
  requestVersion       = HTTP/1.1
}
 ConnectionTimeout
Error: processing vignette 'ssdtools.Rmd' failed with diagnostics:
pandoc document conversion failed with error 61
--- failed re-building ‘ssdtools.Rmd’

--- re-building ‘small-sample-bias.pdf.asis’ using asis
--- finished re-building ‘small-sample-bias.pdf.asis’

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

Error: Vignette re-building failed.
Execution halted

* checking PDF version of manual ... [10s/16s] OK
* checking HTML version of manual ... OK
* checking for non-standard things in the check directory ... OK
* checking for detritus in the temp directory ... OK
* DONE

Status: 1 ERROR
See
  ‘/data/gannet/ripley/R/packages/tests-ATLAS/ssdtools.Rcheck/00check.log’
for details.

Command exited with non-zero status 1
Time 14:45.95, 608.37 + 37.36

[joethorley]

added licensing_md() function which doesn't even use this unstable link.