Comment # 2 on bug 1133809 from Bernhard Wiedemann

Found an unrelated issue with Leap 15's rpm:
rpm --delsign $RPM
left several hundred zeroes in the output.
rpm master and the rpm in SLE-12-SP4 work fine though.

git bisect pointed to this fix:
commit 5c279fb149a44a1bc4d19e11c3c01942732b8486
Author: Panu Matilainen <pmatilai@redhat.com>
Date:   Fri Mar 15 11:43:08 2019 +0200

    Simplify RPMSIGTAG_RESERVEDSPACE shrinking


and the issue might have been originally introduced in
commit 90833a57c523c1a5a074cae81c0c84fb3726fb6d
Author: Lubos Kardos <lkardos@redhat.com>
Date:   Thu May 15 10:15:27 2014 +0200

    Reserve space for gpg signature during building of package.