Bug#1111617: dpkg-dev: dpkg-source --extract fails with sopv-gpgv inline-verify: error: the following arguments are required: CERTS

Hi!

I am running into this same issue:

$ dpkg-source --version
Debian dpkg-source version 1.22.21.
$ dpkg-source --extract bpfcc_0.31.0+ds-7.dsc
usage: sopv-gpgv inline-verify [-h] [--debug] [--not-before TIMESTAMP]
                               [--not-after TIMESTAMP]
                               [--verifications-out VERIFICATIONS]
                               CERTS [CERTS ...]
sopv-gpgv inline-verify: error: the following arguments are required: CERTS
dpkg-source: warning: cannot verify inline signature for
./bpfcc_0.31.0+ds-7.dsc: error code 2
dpkg-source: info: extracting bpfcc in bpfcc-0.31.0+ds
dpkg-source: error: unpack target exists: bpfcc-0.31.0+ds

$ dpkg-source --version
Debian dpkg-source version 1.22.21.
$ dpkg-source --extract bpfcc_0.31.0+ds-7.dsc
dpkg-source: warning: cannot verify inline signature for
./bpfcc_0.31.0+ds-7.dsc: no acceptable signature found
dpkg-source: info: extracting bpfcc in bpfcc-0.31.0+ds
dpkg-source: error: unpack target exists: bpfcc-0.31.0+ds

I read this bug report and also
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1106148 and the
commit attached in this bug report, but I still didn't quite
understand this. Why is it only a warning and why isn't the build
stopped? What is the path to CERTS that should be passed on a regular
Debian unstable system?