"gpg: signing failed: Invalid length" when use brainpool512r1 keys to sign things

[mlnl]

Hi,

>> tested & confirmed with GnuPG 2.2.10, libgcrypt 1.8.3 Debian Stretch 9.5
> 
> Not reproducible here (similar on Debian Stretch).
> 
> I tested with no configuration.
> 
> Is it reproducible under no configuration?
> 
> I tested with:
> 
> 	$ export GNUPGHOME=/tmp/g; mkdir -m=0700 $GNUPGHOME

I have looked at my gpg.conf and found a commented hint for myself ;):
# cert-digest-algo SHA512 for ECC >= 512-bit

Tested again with cert-digest-algo SHA512 without problems:
pub   brainpoolP512r1/0D9032C369992D8E 2018-09-03 [SCA] [verfällt:
2019-09-03]
Schl.-Fingerabdruck = 2601 6E4C BA25 2686 EEC1  EBB8 0D90 32C3 6999 2D8E
  Keygrip = 985D56A2FE62C404CC0382815C391E01B5769F58
uid  testbp512 <testbp512 at test.de>

-- 
mlnl