title: Application error #400 [error:2045] [error:1045] in MantisBT (Ubuntu 18.04)
body: <p>After updating (through -apt update and apt upgrade) access to the installation of MantisBT has become useless. The databases and users are intact.
  Access to the server (VPS) through SSH is available and intact.</p>
  <blockquote>
  <p>The connection to the database has failed. The error returned by the
  database was # 2054: The server requested authentication method
  unknown to the client Use the «Back» button in your web browser to
  return to the previous page. There you can correct the problems that
  have been identified in this error notification or select another
  action. You can also click on an option in the menu bar to go directly
  to a new section.</p>
  </blockquote>
  <p>Error in phpmyadmin:</p>
  <blockquote>
  <p>2054 - The server requested authentication method unknown to the client</p>
  <p>mysqli_real_connect(): The server requested authentication method
  unknown to the client [caching_sha2_password]</p>
  <p>mysqli_real_connect(): (HY000/2054): The server requested
  authentication method unknown to the client</p>
  </blockquote>
  <p><strong>Ubuntu 18.04.2 LTS</strong></p>
  <p><strong>Release: 18.04</strong></p>
  <p><strong>PHP 7.2.15-0ubuntu0.18.04.1 (cli) (built: Feb 8 2019 14:54:22) ( NTS )</strong></p>
  <p><strong>mysql Ver 8.0.15 for Linux on x86_64 (MySQL Community Server - GPL)</strong></p>
  <p><strong>Server version: Apache/2.4.29 (Ubuntu)</strong></p>
  <p>I modified the MySQL configuration:</p>
  <pre><code>ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY 'rootpassword'
  </code></pre>
  <p>but I get the following error:</p>
  <pre><code>ERROR 3009 (HY000): Column count of mysql.user is wrong. Expected 51, found 50. Created with MySQL 80013, now running 80015. Please use mysql_upgrade to fix this error.
  </code></pre>
  <p>When trying to update the MySQL instance:</p>
  <pre><code>mysql_upgrade: Got error: 1045: Access denied for user 'root'@'localhost' (using password: NO) while connecting to the MySQL server
  </code></pre>
  <p>Upgrade process encountered error and will not continue.</p>
  <p><a href="https://i.stack.imgur.com/dfJDo.png" rel="nofollow noreferrer">Error in access page MantisBT</a></p>
  <p><a href="https://i.stack.imgur.com/GAfmL.png" rel="nofollow noreferrer">Error in phpmyadmin</a></p>