title: /bin/login checks passwd despite passing pam account checks
body: <p>To learn the basics of a PAM, I wrote a highly permissive module that returns PAM_SUCCESS for all of the checks (auth, account, password, session). So theoretically, one should be able to login with any username, even those not listed in /etc/passwd, right?</p>
  
  <p>However, it looks like /bin/login performs an account check on its own accord! How do I disable this, so I can let any username login? (for purely theoretical purposes).</p>
  
  <p>My module's log:</p>
  
  <pre><code>pam_sm_authenticate:AUTH request for notinpasswd, allowing it
  pam_sm_acct_mgmt:ACCT request, allowing it
  Invalid user name "notinpasswd" in pam_open:670. Abort.            -- printed by /bin/login
  </code></pre>
  
  <p>Here is my pam.d/other config:</p>
  
  <pre><code>auth      required   pam_open.so
  account   required   pam_open.so
  password  required   pam_open.so
  session   required   pam_open.so
  </code></pre>