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

Quitting from Enhancing_Chemical_Data_Access_with_PubChemR.Rmd:107-109 [unnamed-chunk-9]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<error/rlang_error>
Error in `UseMethod()`:
! no applicable method for 'sectionList' applied to an object of class "NULL"
---
Backtrace:
    ▆
 1. └─PubChemR::sectionList(section)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Error: processing vignette 'Enhancing_Chemical_Data_Access_with_PubChemR.Rmd' failed with diagnostics:
no applicable method for 'sectionList' applied to an object of class "NULL"
--- failed re-building ‘Enhancing_Chemical_Data_Access_with_PubChemR.Rmd’

--- re-building ‘Exploring_Chemical_Data_with_PubChemR.Rmd’ using rmarkdown
[WARNING] Deprecated: --no-highlight. Use --syntax-highlighting=none instead.
--- finished re-building ‘Exploring_Chemical_Data_with_PubChemR.Rmd’

--- re-building ‘Working_with_PubChemR_to_Access_Chemical_Data.Rmd’ using rmarkdown

Quitting from Working_with_PubChemR_to_Access_Chemical_Data.Rmd:955-961 [get_all_sources_substance]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<error/rlang_error>
Error in `value[[3L]]()`:
! Failed to retrieve sources for the specified domain: c(Code = "PUGREST.ServerBusy", Message = "Too many requests or server too busy")
---
Backtrace:
    ▆
 1. └─PubChemR::get_all_sources(domain = "substance")
 2.   └─base::tryCatch(...)
 3.     └─base (local) tryCatchList(expr, classes, parentenv, handlers)
 4.       └─base (local) tryCatchOne(expr, names, parentenv, handlers[[1L]])
 5.         └─value[[3L]](cond)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Error: processing vignette 'Working_with_PubChemR_to_Access_Chemical_Data.Rmd' failed with diagnostics:
Failed to retrieve sources for the specified domain: c(Code = "PUGREST.ServerBusy", Message = "Too many requests or server too busy")
--- failed re-building ‘Working_with_PubChemR_to_Access_Chemical_Data.Rmd’

SUMMARY: processing the following files failed:
  ‘Enhancing_Chemical_Data_Access_with_PubChemR.Rmd’
  ‘Working_with_PubChemR_to_Access_Chemical_Data.Rmd’

Error: Vignette re-building failed.
Execution halted