[pkg-gnupg-maint] Bug#854829: gnupg: tofu-default-policy ask -> Assertion "conflict_set" in get_trust failed

[Benedikt Wildenhain]

Package: gnupg
Version: 2.1.18-3
Severity: normal

Dear Maintainer,

setting "tofu-default-policy ask" in gnupg.conf causes gnupg to crash
when using the --fingerprint command under certain circumstances:

$ gpg --fingerprint
gpg: Ohhhh jeeee: Assertion "conflict_set" in get_trust failed (../../g10/tofu.c:2780)
Aborted

$ gpg --fingerprint  o at b
gpg: Ohhhh jeeee: Assertion "conflict_set" in get_trust failed (../../g10/tofu.c:2780)
Aborted

But:

$ gpg --fingerprint  to at b
pub   [...]

$ gpg --fingerprint  esperanto at benedikt-wildenhain.de
pub   [...]

Kind regards,
Benedikt Wildenhain

-- System Information:
Debian Release: 9.0
  APT prefers testing
  APT policy: (990, 'testing'), (500, 'unstable'), (500, 'stable'), (500, 'oldstable'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.9.0-1-amd64 (SMP w/2 CPU cores)
Locale: LANG=fr_BE.UTF-8, LC_CTYPE=fr_BE.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages gnupg depends on:
ii  gnupg-agent    2.1.18-3
ii  libassuan0     2.4.3-2
ii  libbz2-1.0     1.0.6-8.1
ii  libc6          2.24-9
ii  libgcrypt20    1.7.6-1
ii  libgpg-error0  1.26-2
ii  libksba8       1.3.5-2
ii  libreadline7   7.0-2
ii  libsqlite3-0   3.16.2-2
ii  zlib1g         1:1.2.8.dfsg-5

Versions of packages gnupg recommends:
ii  dirmngr     2.1.18-3
ii  gnupg-l10n  2.1.18-3

Versions of packages gnupg suggests:
ii  parcimonie  0.10.2-4
ii  xloadimage  4.1-24

-- no debconf information