[Rd] failed check in reg-tests-1b.R

[Benjamin Tyner]

Not certain this is actually a bug, so posting here.

I'm on Ubuntu 18.04.4 LTS, building R version 4.0.0. The "configure" and 
"make" steps are successful, but the "make check" step fails when it 
gets to this part of ./tests/reg-tests-1b.R:

    > ## methods() gave two wrong warnings in some cases:
    > op <- options(warn = 2)# no warning, please!
    > m1 <- methods(na.omit) ## should give (no warning):
    > ##
    > setClass("bla")
    > setMethod("na.omit", "bla", function(object, ...) "na.omit(<bla>)")
    Error: package 'codetools' was installed before R 4.0.0: please 
re-install it
    Execution halted

It appears to be picking up the older version of codetools from $R_LIBS; 
if I unset R_LIBS, then it works just fine.

So I'm wondering, is it a bug, or is the user's own fault for having 
R_LIBS set whilst trying to build R?

Regards,

Ben