bug/oversight in TestLib.pm and PostgresNode.pm

I am trying to re-create pgbench-over-logical-replication as a TAP-test.
(the wisdom of that might be doubted, and I appreciate comments on it
too, but it's really another subject).

While trying to test pgbench's stderr (looking for 'creating tables' in
output of the initialisation step) I ran into these two bugs (or
perhaps better 'oversights').

But especially the omission of command_fails_like() in PostgresNode.pm
feels like an bug.

In the end it was necessary to change TestLib.pm's command_like()
because command_fails_like() also checks for a non-zero return value
(which seems to make sense, but in this case not possible: pgbench
returns 0 on init with output on stderr).

make check-world passes without error

Thanks,

Erik Rijkers