dpkg: dependency problems prevent configuration of mysql-server:
 mysql-server depends on mysql-server-5.7; however:
   Package mysql-server-5.7 is not configured yet.

dpkg: error processing package mysql-server (--configure):
 dependency problems - leaving unconfigured
...

...
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Errors were encountered while processing:
 mysql-server-5.7
 mysql-server
E: Sub-process /usr/bin/dpkg returned an error code (1)