Key import issues

[A.L.E.C]

A few users have (different) problems with importing secret keys
generated by OpenPGP.js. For me it works. Could anyone explain why gpg
exits with code 2 and what exactly these errors mean?

(gnupg 2.0.28 in this case)
ERROR: gpg: key FF0A6901: secret key imported
ERROR: gpg: assuming bad signature from key FF0A6901 due to an unknown
critical bit
ERROR: gpg: key FF0A6901: no valid user IDs
ERROR: gpg: this may be caused by a missing self-signature
ERROR: gpg: Total number processed: 1
ERROR: gpg: w/o user IDs: 1
ERROR: gpg: secret keys read: 1
ERROR: gpg: secret keys imported: 1
STATUS: IMPORT_OK 17 91FABCEE268FE9727BC116A43F4D44C4FF0A6901
STATUS: IMPORT_RES 1 1 0 0 0 0 0 0 0 1 1 0 0 0

(gnupg 2.0.29 for this case)
ERROR: gpg: key 0D20E76A: secret key imported
ERROR: gpg: key 0D20E76A was created 31 seconds in the future (time warp
or clock problem)
ERROR: gpg: key 0D20E76A: no valid user IDs
ERROR: gpg: this may be caused by a missing self-signature
ERROR: gpg: Total number processed: 1
ERROR: gpg:           w/o user IDs: 1
ERROR: gpg:       secret keys read: 1
ERROR: gpg:   secret keys imported: 1
STATUS: IMPORT_OK 17 3DDABF41C0AA422971DA1258C47F2A380D20E76A
STATUS: IMPORT_RES 1 1 0 0 0 0 0 0 0 1 1 0 0 0


-- 
Aleksander 'A.L.E.C' Machniak
Kolab Groupware Developer         [http://kolab.org]
Roundcube Webmail Developer   [http://roundcube.net]
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PGP: 19359DC1 # Blog: https://kolabian.wordpress.com