The macro %_signature in /usr/lib/rpm/macros does not get
overriden by %_signature in ~/.rpmmacros. The default in
/usr/lib/rpm/macros being none, a ~/.rpmmacros of pgp will
not sign rpms with pgp.
I verified that %_signature can be set in ~/.rpmmacros
by setting an invalid value (e.g. %_signature XXXX) in ~/.rpmmacros.
This gives the expected error
Invalid %_signature spec in macro file.
when attempting to sign idicating that ~/.rpmmacros is indeed the
final place in which %_signature will be set.
Please reopen if you (or someone else) can reproduce this
problem - I don't know how to.