Error in install.packages : unknown input format

[Eric Kernfeld]

Has anyone encountered an error where virtually every package installation is met with "Error in install.packages : unknown input format"? To reproduce this, I can simply open Rstudio in a project using Packrat, then run `install.packages("ggplot2")` twice. The second time it will err as stated. It continues to err even if I turn `packrat::off()`.

I thought it might be an Rstudio problem, so I updated Rstudio, but it persists. I think it's a packrat problem because the installation works fine (at least the first, second, and third time) in any session where I am not using packrat. 

[Eric Kernfeld]

Since I get one free pass per session, I worked around this bug for now by terminating my R session prior to each new package I want to install. For a package with dependencies, I manually installed the dependencies first. For example, to install velocyto.R, I terminated R, installed pcaMethods and another dependency, then terminated R. Then, devtools::install_github did not work (maybe a separate issue), so I downloaded the source to a local repo, used packrat::set_opts to point packrat to the local repo, and finally did `packrat::install_local("velocyto.R")`.