While running cookbook with chef-vault I'm getting this error.
FYI,
knife vault create user_password sunil --json ./sunil_password.json ':'
knife data bag from file user_password user_password/sunil.json
knife data bag from file user_password user_password/sunil_keys.json
Chef User name :sunil_chef
Data Bags and Vaults are different things. You have to either create and upload a vault OR a data bag. I don't know where your file user_password/sunil_keys.json and user_password/sunil.json are from, but the general steps for you are:
Make sure your knife.rb contains knife[:vault_mode] = 'client'
Create a JSON with the contents you want in the Vault (probably this is user_password/sunil.json)
Delete the DataBag you currently have with knife data bag delete user_password
Create the vault passing your admin user, the node name that should have access and the json. Something like knife vault create user_password sunil -C "<list of nodes that should have access here>" -A "sunil_chef" --file user_password/sunil.json