Build via devtools does not work

[CDieterich]

install_github("dieterich-lab/JACUSA2helper", build_vignettes = TRUE)
...
SUMMARY: processing the following file failed:
'JACUSA2helper-nanopore.Rmd'

Fehler: Vignette re-building failed.
Ausf"uhrung angehalten
Fehler: Failed to install 'JACUSA2helper' from GitHub:
System command 'R' failed, exit status: 1, stdout + stderr (last 10 lines):
E> --- failed re-building 'JACUSA2helper-nanopore.Rmd'
E>
E> --- re-building 'JACUSA2helper.Rmd' using rmarkdown
E> --- finished re-building 'JACUSA2helper.Rmd'
E>
E> SUMMARY: processing the following file failed:
E> 'JACUSA2helper-nanopore.Rmd'
E>
E> Fehler: Vignette re-building failed.
E> Ausf"uhrung angehalten

[CDieterich]

I am running R4.0.2