KeyManager API do not follows specification when importing keys.

[cheatfate]

This keystore request could not be processed by nimbus keystore manager api.

{"keystores": ["{\"crypto\": {\"kdf\": {\"function\": \"scrypt\", \"params\": {\"dklen\": 32, \"n\": 262144, \"r\": 8, \"p\": 1, \"salt\": \"zzz\"}, \"message\": \"\"}, \"checksum\": {\"function\": \"sha256\", \"params\": {}, \"message\": \"zzz\"}, \"cipher\": {\"function\": \"aes-128-ctr\", \"params\": {\"iv\": \"a24857026939492f49444679544cb6bb\"}, \"message\": \"zzzz\"}}, \"description\": \"\", \"pubkey\": \"zzzz\", \"path\": \"m/12381/3600/0/0/0\", \"uuid\": \"1ea9ed13-e3bb-4555-99d9-c5e83ab9eb67\", \"version\": 4}"], "passwords": ["MyTestPassword"]}

keystores array should be filled with strings, not objects.
https://github.com/ethereum/keymanager-APIs/blob/master/types/keystore.yaml

[cheatfate]

slashing_protection should be treated as json string too.