GNUPG2 suddenly throwing "Error building skey array: No such file or directory"

Some context: I'm a maintainer for a project which uses gnupg2 as part of a framework to encrypt data with a PGP public key so it can't be read if our severs are ever breached, my CI script has worked fine up until today where I got a strange error message:

Inappropriate ioctl for device

I fixed this by adding the following line to my CI script (which worked)

export GPG_TTY=$(tty)

However I'm now running into an issue where it just randomly throws the error:

Error building skey array: No such file or directory

Does anyone know why this error might be occurring or what file or directory it is unable to find? I found online that the following directories might be missing or have invalid permissions but it didn't seem to do anything:

$ mkdir -p ~/.gnupg/private-keys-v1.d
$ chmod 700 ~/.gnupg/private-keys-v1.d

The following is the output of my CI runner:

$ export GPG_TTY=$(tty)
$ apt-get update
Get:1 http://security.debian.org/debian-security stretch/updates InRelease [94.3 kB]
Get:3 http://security.debian.org/debian-security stretch/updates/main amd64 Packages [440 kB]
Ign:2 http://cdn-fastly.deb.debian.org/debian stretch InRelease
Get:4 http://cdn-fastly.deb.debian.org/debian stretch-updates InRelease [91.0 kB]
Get:5 http://cdn-fastly.deb.debian.org/debian stretch Release [118 kB]
Get:6 http://cdn-fastly.deb.debian.org/debian stretch Release.gpg [2434 B]
Get:7 http://cdn-fastly.deb.debian.org/debian stretch-updates/main amd64 Packages [12.1 kB]
Get:8 http://cdn-fastly.deb.debian.org/debian stretch/main amd64 Packages [9530 kB]
Fetched 10.3 MB in 4s (2169 kB/s)
Reading package lists...
$ apt-get install -y zip gnupg2
Reading package lists...
Building dependency tree...
Reading state information...
The following additional packages will be installed:
  unzip
The following NEW packages will be installed:
  gnupg2 unzip zip
0 upgraded, 3 newly installed, 0 to remove and 9 not upgraded.
Need to get 703 kB of archives.
After this operation, 1486 kB of additional disk space will be used.
Get:1 http://cdn-fastly.deb.debian.org/debian stretch/main amd64 gnupg2 all 2.1.18-8~deb9u1 [299 kB]
Get:2 http://cdn-fastly.deb.debian.org/debian stretch/main amd64 unzip amd64 6.0-21 [170 kB]
Get:3 http://cdn-fastly.deb.debian.org/debian stretch/main amd64 zip amd64 3.0-11+b1 [234 kB]
debconf: delaying package configuration, since apt-utils is not installed
Fetched 703 kB in 1s (528 kB/s)
Selecting previously unselected package gnupg2.
(Reading database ... 
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(Reading database ... 29828 files and directories currently installed.)
Preparing to unpack .../gnupg2_2.1.18-8~deb9u1_all.deb ...
Unpacking gnupg2 (2.1.18-8~deb9u1) ...
Selecting previously unselected package unzip.
Preparing to unpack .../unzip_6.0-21_amd64.deb ...
Unpacking unzip (6.0-21) ...
Selecting previously unselected package zip.
Preparing to unpack .../zip_3.0-11+b1_amd64.deb ...
Unpacking zip (3.0-11+b1) ...
Processing triggers for mime-support (3.60) ...
Setting up unzip (6.0-21) ...
Setting up zip (3.0-11+b1) ...
Setting up gnupg2 (2.1.18-8~deb9u1) ...
$ echo "$GPG_PUBLIC_KEY" | gpg --import
gpg: WARNING: unsafe permissions on homedir '/root/.gnupg'
gpg: keybox '/root/.gnupg/pubring.kbx' created
gpg: /root/.gnupg/trustdb.gpg: trustdb created
gpg: key REDACTED: public key "REACTED <redacted@redacted >" imported
gpg: Total number processed: 1
gpg:               imported: 1
$ echo "$GPG_PRIVATE_KEY" | gpg --import
gpg: WARNING: unsafe permissions on homedir '/root/.gnupg'
gpg: key REDACTED: "REACTED <redacted@redacted>" not changed
gpg: key REDACTED/REDACTED: error sending to agent: No such file or directory
gpg: error building skey array: No such file or directory
gpg: Total number processed: 1
gpg:              unchanged: 1
gpg:       secret keys read: 1
ERROR: Job failed: exit code 1

I set up my docker as follows:

$ docker pull python:latest
$ docker create python:latest --name python
$ docker run -it python /bin/bash

The following is the most recent place I've managed to find this error in the last year:

• https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=867783

Solution 1:

Turns out it was an issue with a newer version of GNUPG2, I fixed the issue by adding the --batch flag to gpg --import (based off of this question)

Fixed line of code:

echo "$GPG_PRIVATE_KEY" | gpg --batch --import