'Convenience method that provides a quick way to add an email grant
to a key. This method retrieves the current ACL, creates a new
grant based on the parameters passed in, adds that grant to the ACL
and then PUT\'s the new ACL back to S3.
:type permission: string
:param permission: The permission being granted. Should be one of:
(READ, WRITE, READ_ACP, WRITE_ACP, FULL_CONTROL).
:type email_address: string
:param email_address: The email address associated with the AWS
account your are granting the permission to.
:type recursive: boolean
:param recursive: A boolean value to controls whether the
command will apply the grant to all keys within the bucket
or not.  The default value is False.  By passing a True
value, the call will iterate through all keys in the
bucket and apply the same grant to each key.  CAUTION: If
you have a lot of keys, this could take a long time!'

def add_email_grant(self, permission, email_address, headers=None):

    policy = self.get_acl(headers=headers)
    policy.acl.add_email_grant(permission, email_address)
    self.set_acl(policy, headers=headers)
