check for compatible version of python when building vignette (#1138)
check for compatible version of python when building vignette (#1138)

* check for compatible version of python when building vignette

* check for numpy as well

* require python 3.8
rstudio/reticulate,rstudio/reticulate,rstudio/reticulate,rstudio/reticulate,rstudio/reticulate