[Rd] Bug in R CMD INSTALL when handling invalid LazyData DESCRIPTION field

[Aaron Wells]

Hi, I think I've found a bug in R CMD INSTALL. When it tries to parse a
DESCRIPTION file with an invalid LazyData field, it errors out while
trying to print the correct error message:

> R CMD INSTALL .
* installing to library ‘/home/example/R/x86_64-pc-linux-gnu-library/3.4’
* installing *source* package ‘samplepackage’ ...
** data
Error in errmsg("invalid value of ", field, " field in DESCRIPTION") :
  could not find function "errmsg"
* removing ‘/home/example/R/x86_64-pc-linux-gnu-library/3.4/samplepackage’


It should instead be using that errmsg() function to print the more
helpful error message: "invalid value of LazyData field in DESCRIPTION".

I've traced it down to this line of code in tools:::.install_packages()
https://github.com/wch/r-source/blob/trunk/src/library/tools/R/install.R#L977
. The errmsg() function actually is defined earlier on in the function,
but there seems to be a scoping issue that makes it not available here.

I've uploaded a sample project to reproduce the bug here:
https://github.com/agwells/R-CMD-INSTALL-bug

I'm running R version 3.4.2 (2017-09-28), on Ubuntu 16.04.

Cheers,
Aaron