Most contemporary shells execute each command of a multi-command
pipeline in a subshell environment.  Environment variables set inside a
subshell do not affect the parent shell's environment.  Meanwhile, the
rrchecker system test sets the ret variable inside a while loop which is
the last command in a pipeline.  Thus, while error messages will be
printed out when named-rrchecker encounters a problem, these problems
will not affect the result of the system test.

This issue seems to be have been present in the code ever since
named-rrchecker was added by commit 49c1e0d18d.