🚧 touch up Authenticator

lib/net/imap/sasl/authenticator.rb

@@ -106,6 +106,7 @@ module SASL
       # * +scram_sha1_salted_passwords+, +scram_sha256_salted_password+ ---
       #   Salted password(s) (with salt and iteration count) for the +SCRAM-*+
       #   mechanism family.  <tt>[salt, iterations, pbkdf2_hmac]</tt> tuple.
+      #   <em>(not implemented yet...)</em>
       # * +passcode+ --- passcode for SecurID 2FA <em>(not implemented)</em>
       # * +pin+ --- Personal Identification number, e.g. for SecurID 2FA
       #   <em>(not implemented)</em>
@@ -306,7 +307,7 @@ def initialize(*, **, &callback)
         # See PlainAuthenticator or DigestMD5Authenticator for example
         # authenticator implementations.
         def process(server_challenge_string)
-          raise NoMethodError, "#{__method__} is defined by subclasses"
+          raise NotImplementedError, "#{__method__} is defined by subclasses"
         end
 
         # :call-seq: