git tag v4.4.0 verify failed with 'No public key'

[Dongsheng Song]

# git tag -v v4.4.0
object 9ee45dd09766204be7d94a399290123f72b3c75f
type commit
tag v4.4.0
tagger Justin C. Sherrill <justin at shiningsilence.com> 1449187115 -0500

DragonFly 4.4.0
gpg: Signature made Fri Dec  4 07:58:35 2015 CST using RSA key ID 8B01DD89
gpg: Can't check signature: No public key
error: could not verify the tag 'v4.4.0'

I can not found the key in pgp.mit.edu or pool.sks-keyservers.net, both of
them report:
  No results found: No keys found
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