unable to connect R-devel-el-capitan-signed.pkg

Dear colleagues,
I found that for:

language: r
os: osx

is unable to connect to https://r.research.att.com/el-capitan/R-devel/R-devel-el-capitan-signed.pkg (because the file does not exist, only R-devel-el-capitan.pkg).
Is it possible to fix it somehow?
Many thanks
Vojtech Spiwok

There’s another thread about the same issue: R-devel-el-capitan-signed.pkg fails to download when testing on R devel