Unable to migrate a database: Unknown collation: 'utf8_unicode_520_ci'

Symptoms

• Unable to migrate a database. The following error is displayed in Plesk:

  PLESK_ERROR: Failed to copy content of database 'wordpress_v'
  Migration tools tried to perform operation in 1 attempts: Restoration of MySQL database failed. Most probable reason:
  Target MySQL server does not contain necessary character set.
  Most likely it is required to have at least MySQL 5.5 to restore such database.
  Here is the original error message reported by MySQL client when restoring the database:
  ERROR 1273 (HY000) at line 25: Unknown collation: 'utf8mb4_unicode_520_ci'

• In the migration debug.log file:

  CONFIG_TEXT: Here is the original error message reported by MySQL client when restoring the database:
  ERROR 1273 (HY000) at line 177: Unknown collation: 'utf8mb4_unicode_520_ci'

• The following errors may be reported:

  CONFIG_TEXT: ERROR 1273 (HY000) at line 25: Unknown collation: 'utf8_unicode_520_ci'
  ERROR 1273 (HY000) at line 25: Unknown collation: 'utf8mb4_unicode_520_ci'

• MySQL version installed on the destination server is 5.5.x:

  # plesk db -Ne "select version()"
  5.5.56-MariaDB

• Required collations are not available on current MySQL version:

  # plesk db -e "show collation" | grep utf8*.*_unicode_520
  #

Cause

On the target server, MySQL can not install the required collation.

Resolution

Migrate the account to a destination server with the same MySQL version as on the source server.

Or

Upgrade MariaDB to the 10.1 version on the destination server. Instructions are available at How to upgrade MySQL 5.5 to 5.6/5.7 or MariaDB 5.5 to 10.0/10.1/10.2 on Linux.