Cannot install on Google Colaboratory

Summary:

RStan installation on Google Colaboratory now fails.

Description:

"apt install r-cran-rstan" suddenly stopped working. On Google Colaboratory, the following script is expected to set up a working RStan environment, as described in Installing RStan on Linux.

system("add-apt-repository -y ppa:marutter/c2d4u3.5")
system("apt update")
system("apt install r-cran-rstan")

However, the last step now fails, so the following "library(rstan)" also fails.

Reproducible Steps:

Open a notebook with: https://colab.research.google.com/notebook#create=true&language=r

Run the following code:

system("add-apt-repository -y ppa:marutter/c2d4u3.5")
system("apt update")
system("apt install r-cran-rstan",TRUE)

Current Output:

Warning message in system("apt install r-cran-rstan", TRUE):
"running command 'apt install r-cran-rstan' had status 100"
'Reading package lists...'
'Building dependency tree...'
'Reading state information...'
'Some packages could not be installed. This may mean that you have'
'requested an impossible situation or if you are using the unstable'
'distribution that some required packages have not yet been created'
'or been moved out of Incoming.''The following information may help to resolve the situation:'
''
'The following packages have unmet dependencies:'
' r-cran-rstan : Depends: r-cran-v8 but it is not going to be installed'

R Version:

R version 3.6.3 (2020-02-29)

Operating System:

Running on Google Colaboratory with IRkernel

Start with the Google Colaboratory notebook and the installation commands in the issue, then inspect why apt cannot install the r-cran-v8 dependency required by r-cran-rstan. Compare the environment with the Installing RStan on Linux wiki instructions. Done means the installation completes and library(rstan) loads successfully in Colab.