t7004-tag.sh fails (old gpg?)

t7004-tag.sh fails for me:

* expecting success: 
        git-tag -s -m "A signed tag message" signed-tag &&
        get_tag_msg signed-tag >actual &&
        git-diff expect actual

gpg: Warning: using insecure memory!
gpg: [don't know]: invalid packet (ctb=00)
gpg: read_keyblock: read error: invalid packet
gpg: enum_keyblocks failed: invalid keyring
gpg: skipped `C O Mitter <committer@example.com>': invalid keyring
gpg: signing failed: invalid keyring
failed to sign the tag with GPG.
* FAIL 49: creating a signed tag with -m message should succeed

                git-tag -s -m "A signed tag message" signed-tag &&
                get_tag_msg signed-tag >actual &&
                git-diff expect actual

I see that you alread check for presence of gpg, but maybe you should also check that it is recent enough. This is the version I have:

bash-3.00$ gpg --version gpg (GnuPG) 1.0.6 Copyright (C) 2001 Free Software Foundation, Inc. This program comes with ABSOLUTELY NO WARRANTY. This is free software, and you are welcome to redistribute it under certain conditions. See the file COPYING for details.

Home: ~/.gnupg
Supported algorithms:
Cipher: 3DES, CAST5, BLOWFISH, RIJNDAEL, RIJNDAEL192, RIJNDAEL256, TWOFISH
Pubkey: RSA, RSA-E, RSA-S, ELG-E, DSA, ELG
Hash: MD5, SHA1, RIPEMD160

skimo