Occasional CRAN ERROR when compiling vignette with pandoc on MacOS (x86) probably due to low memory

[trevorld]

• Only seems to affect MacOS x86 CRAN machine
• This ERROR was gone for a while but seems to have returned
• Web searching the "error 127" suggests the CRAN checker doesn't have enough memory
• In 2017 I sent an e-mail to Simon Urbanek suggesting he set the --no-vignettes (no response) for the relevant machines
• I've not been able to reproduce this on the OSX machines using Github Actions (or previously with Travis CI)---the vignette always compiles fine
• CRAN output:

Version: 1.7.4
Check: re-building of vignette outputs
Result: ERROR
  Error(s) in re-building vignettes:
    ...
  --- re-building ‘optparse.Rrst’ using knitr
  sh: +RTS: command not found
  Warning in system(command) : error in running command
  Error: processing vignette 'optparse.Rrst' failed with diagnostics:
  pandoc document conversion failed with error 127
  --- failed re-building ‘optparse.Rrst’
  
  SUMMARY: processing the following file failed:
    ‘optparse.Rrst’
  
  Error: Vignette re-building failed.
  Execution halted
Flavor: r-release-macos-x86_64