The unit tests in my project, https://github.com/vsajip/python-gnupg, have started failing following an upgrade to GnuPG 2.2.33. Previously with 2.2.32, there were no failures. With 2.3.3, there are no failures either, so it does seem like a regression. Tests were run on Linux Mint 19.1 (based on Ubuntu bionic) 64-bit.
Below are sections in my test log showing the failures:
Failure 1:
```
DEBUG gnupg MainThread 967 27322: gpg2 --status-fd 2 --no-tty --no-verbose --fixed-list-mode --batch --with-colons --homedir /tmp/keys-c_alhlfn --debug-quick-random --encrypt --recipient 99BFC3DB10FE4BE821EA1228EF574800D803274C --recipient 9E26CD705E8C31F39A0E7E1C9BFFF293021B7D5E --armor
DEBUG gnupg MainThread 173 data copier: <Thread(Thread-45 (_copy_data), initial daemon)>, <_io.BytesIO object at 0x7f9d27c5ba10>, <_io.BufferedWriter name=5>
DEBUG gnupg MainThread 1029 stderr reader: <Thread(Thread-46 (_read_response), initial daemon)>
DEBUG gnupg Thread-45 (_copy_data) 168 closed output, 13 bytes sent
DEBUG gnupg MainThread 1036 stdout reader: <Thread(Thread-47 (_read_data), initial daemon)>
DEBUG gnupg Thread-46 (_read_response) 985 [GNUPG:] KEY_CONSIDERED 9E26CD705E8C31F39A0E7E1C9BFFF293021B7D5E 0
DEBUG gnupg Thread-46 (_read_response) 985 [GNUPG:] KEY_CONSIDERED 99BFC3DB10FE4BE821EA1228EF574800D803274C 0
DEBUG gnupg Thread-46 (_read_response) 985 gpg: 8A3A613F82AAD7CD: There is no assurance this key belongs to the named user
DEBUG gnupg Thread-46 (_read_response) 985 [GNUPG:] INV_RECP 10 99BFC3DB10FE4BE821EA1228EF574800D803274C
DEBUG gnupg Thread-46 (_read_response) 985 [GNUPG:] FAILURE encrypt 53
DEBUG gnupg Thread-46 (_read_response) 985 gpg: [stdin]: encryption failed: Unusable public key
WARNING gnupg MainThread 1046 gpg returned a non-zero error code: 2
```
Failure 2:
```
DEBUG gnupg MainThread 967 27422: gpg2 --status-fd 2 --no-tty --no-verbose --fixed-list-mode --batch --with-colons --homedir /tmp/keys-2819fmm4 --debug-quick-random --encrypt --recipient F3C987C36C5C6343C9A5D5A1A3F494F6028E4866 --recipient FB61B9109C3DE42A98E9A3C2877E2F37005A7B82 --armor
DEBUG gnupg MainThread 173 data copier: <Thread(Thread-92 (_copy_data), initial daemon)>, <_io.BytesIO object at 0x7f9d27cd0860>, <_io.BufferedWriter name=5>
DEBUG gnupg MainThread 1029 stderr reader: <Thread(Thread-93 (_read_response), initial daemon)>
DEBUG gnupg Thread-92 (_copy_data) 168 closed output, 12 bytes sent
DEBUG gnupg MainThread 1036 stdout reader: <Thread(Thread-94 (_read_data), initial daemon)>
DEBUG gnupg Thread-93 (_read_response) 985 [GNUPG:] KEY_CONSIDERED FB61B9109C3DE42A98E9A3C2877E2F37005A7B82 2
DEBUG gnupg Thread-93 (_read_response) 985 gpg: checking the trustdb
DEBUG gnupg Thread-93 (_read_response) 985 [GNUPG:] KEY_CONSIDERED FB61B9109C3DE42A98E9A3C2877E2F37005A7B82 0
DEBUG gnupg Thread-93 (_read_response) 985 gpg: marginals needed: 3 completes needed: 1 trust model: pgp
DEBUG gnupg Thread-93 (_read_response) 985 gpg: depth: 0 valid: 1 signed: 0 trust: 0-, 0q, 0n, 0m, 0f, 1u
DEBUG gnupg Thread-93 (_read_response) 985 [GNUPG:] KEY_CONSIDERED F3C987C36C5C6343C9A5D5A1A3F494F6028E4866 2
DEBUG gnupg Thread-93 (_read_response) 985 gpg: A3F494F6028E4866: There is no assurance this key belongs to the named user
DEBUG gnupg Thread-93 (_read_response) 985 [GNUPG:] INV_RECP 10 F3C987C36C5C6343C9A5D5A1A3F494F6028E4866
DEBUG gnupg Thread-93 (_read_response) 985 [GNUPG:] FAILURE encrypt 53
DEBUG gnupg Thread-93 (_read_response) 985 gpg: [stdin]: encryption failed: Unusable public key
WARNING gnupg MainThread 1046 gpg returned a non-zero error code: 2
```
Failure 3:
```
DEBUG gnupg MainThread 967 27924: gpg2 --status-fd 2 --no-tty --no-verbose --fixed-list-mode --batch --with-colons --homedir /tmp/keys-9z49t40e --debug-quick-random --verify
DEBUG gnupg MainThread 173 data copier: <Thread(Thread-320 (_copy_data), initial daemon)>, <_io.BytesIO object at 0x7f9d27c5a160>, <_io.BufferedWriter name=5>
DEBUG gnupg MainThread 1029 stderr reader: <Thread(Thread-321 (_read_response), initial daemon)>
DEBUG gnupg Thread-320 (_copy_data) 168 closed output, 256 bytes sent
DEBUG gnupg MainThread 1036 stdout reader: <Thread(Thread-322 (_read_data), initial daemon)>
DEBUG gnupg Thread-321 (_read_response) 985 [GNUPG:] NEWSIG
DEBUG gnupg Thread-321 (_read_response) 378 message ignored: NEWSIG,
DEBUG gnupg Thread-321 (_read_response) 985 gpg: Signature made Sun 19 Dec 2021 12:29:05 GMT
DEBUG gnupg Thread-321 (_read_response) 985 gpg: using DSA key FA9FB0DFE0431A24BF6942AFFA493F5794378D15
DEBUG gnupg Thread-321 (_read_response) 985 [GNUPG:] KEY_CONSIDERED FA9FB0DFE0431A24BF6942AFFA493F5794378D15 0
DEBUG gnupg Thread-321 (_read_response) 378 message ignored: KEY_CONSIDERED, FA9FB0DFE0431A24BF6942AFFA493F5794378D15 0
DEBUG gnupg Thread-321 (_read_response) 985 [GNUPG:] SIG_ID naHfhoqnNFwY4NFn3LuKeuZHFXY 2021-12-19 1639916945
DEBUG gnupg Thread-321 (_read_response) 985 [GNUPG:] KEY_CONSIDERED FA9FB0DFE0431A24BF6942AFFA493F5794378D15 0
DEBUG gnupg Thread-321 (_read_response) 378 message ignored: KEY_CONSIDERED, FA9FB0DFE0431A24BF6942AFFA493F5794378D15 0
DEBUG gnupg Thread-321 (_read_response) 985 gpg: checking the trustdb
DEBUG gnupg Thread-321 (_read_response) 985 gpg: no ultimately trusted keys found
DEBUG gnupg Thread-321 (_read_response) 985 [GNUPG:] GOODSIG FA493F5794378D15 Andrew Able (A test user (insecure!)) <andrew.able@alpha.com>
DEBUG gnupg Thread-321 (_read_response) 985 gpg: Good signature from "Andrew Able (A test user (insecure!)) <andrew.able@alpha.com>" [unknown]
DEBUG gnupg Thread-321 (_read_response) 985 [GNUPG:] VALIDSIG FA9FB0DFE0431A24BF6942AFFA493F5794378D15 2021-12-19 1639916945 0 4 0 17 2 01 FA9FB0DFE0431A24BF6942AFFA493F5794378D15
DEBUG gnupg Thread-321 (_read_response) 985 [GNUPG:] KEY_CONSIDERED FA9FB0DFE0431A24BF6942AFFA493F5794378D15 0
DEBUG gnupg Thread-321 (_read_response) 378 message ignored: KEY_CONSIDERED, FA9FB0DFE0431A24BF6942AFFA493F5794378D15 0
DEBUG gnupg Thread-321 (_read_response) 985 [GNUPG:] TRUST_UNDEFINED 0 pgp
DEBUG gnupg Thread-321 (_read_response) 985 gpg: WARNING: This key is not certified with a trusted signature!
DEBUG gnupg Thread-321 (_read_response) 985 gpg: There is no indication that the signature belongs to the owner.
DEBUG gnupg Thread-321 (_read_response) 985 Primary key fingerprint: FA9F B0DF E043 1A24 BF69 42AF FA49 3F57 9437 8D15
```
Note: all keys are transient, created in the tests. You should be able to reproduce these results by cloning https://github.com/vsajip/python-gnupg and then running
GPGBINARY=/path/to/gpg-2.2.33 test_gnupg.py and looking at the created `test_gnupg.log`.