Error(s) in re-building vignettes:
  ...
--- re-building 'checkpoint.Rmd' using rmarkdown
* installing *source* package 'darts' ...
staged installation is only possible with locking
** using non-staged installation
** libs
make[1]: Entering directory '/tmp/RtmpDSxikQ/R.INSTALL252d5b5e0f31/darts/src'
clang-9 -I"/home/hornik/tmp/R.check/r-devel-clang/Work/build/include" -DNDEBUG   -I/usr/local/include -D_FORTIFY_SOURCE=2  -fpic  -g -O3 -Wall -pedantic -mtune=native -c darts.c -o darts.o
clang-9 -shared -L/home/hornik/tmp/R.check/r-devel-clang/Work/build/lib -Wl,-O1 -o darts.so darts.o -L/home/hornik/tmp/R.check/r-devel-clang/Work/build/lib -lR
make[1]: Leaving directory '/tmp/RtmpDSxikQ/R.INSTALL252d5b5e0f31/darts/src'
make[1]: Entering directory '/tmp/RtmpDSxikQ/R.INSTALL252d5b5e0f31/darts/src'
make[1]: Leaving directory '/tmp/RtmpDSxikQ/R.INSTALL252d5b5e0f31/darts/src'
installing to /tmp/RtmpGu41YK/.checkpoint/2017-04-01/lib/x86_64-pc-linux-gnu/4.0.0/darts/libs
** R
** byte-compile and prepare package for lazy loading
** help
*** installing help indices
** building package indices
** testing if installed package can be loaded
* DONE (darts)
Warning in file(con, "w") :
  cannot open file '/tmp/RtmpGu41YK/rmarkdown-str75a741e94db6.html': No such file or directory
Error: processing vignette 'checkpoint.Rmd' failed with diagnostics:
cannot open the connection
--- failed re-building 'checkpoint.Rmd'

--- re-building 'managing-checkpoint-archives.Rmd' using rmarkdown

checkpoint: Part of the Reproducible R Toolkit from Microsoft
https://mran.microsoft.com/documents/rro/reproducibility/
Scanning for packages used in this project
- Discovered 1 packages
Installing packages used in this project 
 - Installing 'darts'
darts
* installing *source* package 'darts' ...
staged installation is only possible with locking
** using non-staged installation
** libs
make[1]: Entering directory '/tmp/RtmpdpQ9Gz/R.INSTALL5af87f751416/darts/src'
clang-9 -I"/home/hornik/tmp/R.check/r-devel-clang/Work/build/include" -DNDEBUG   -I/usr/local/include -D_FORTIFY_SOURCE=2  -fpic  -g -O3 -Wall -pedantic -mtune=native -c darts.c -o darts.o
clang-9 -shared -L/home/hornik/tmp/R.check/r-devel-clang/Work/build/lib -Wl,-O1 -o darts.so darts.o -L/home/hornik/tmp/R.check/r-devel-clang/Work/build/lib -lR
make[1]: Leaving directory '/tmp/RtmpdpQ9Gz/R.INSTALL5af87f751416/darts/src'
make[1]: Entering directory '/tmp/RtmpdpQ9Gz/R.INSTALL5af87f751416/darts/src'
make[1]: Leaving directory '/tmp/RtmpdpQ9Gz/R.INSTALL5af87f751416/darts/src'
installing to /tmp/RtmpZyFeIs/.checkpoint/2015-04-26/lib/x86_64-pc-linux-gnu/4.0.0/darts/libs
** R
** byte-compile and prepare package for lazy loading
** help
*** installing help indices
** building package indices
** testing if installed package can be loaded
* DONE (darts)
checkpoint process complete
---
--- finished re-building 'managing-checkpoint-archives.Rmd'

SUMMARY: processing the following file failed:
  'checkpoint.Rmd'

Error: Vignette re-building failed.
Execution halted