I thought it might have been an old mysql 5.6 config file that was incompatible so I did the following (still unresolved):

:~$ sudo mv /etc/mysql/ /etc/mysql-backup

:~$ sudo apt-get remove --purge mysql-server mysql-server-5.7
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages were automatically installed and are no longer required:
  mysql-client-5.7 mysql-client-core-5.7 mysql-server-core-5.7
Use 'sudo apt autoremove' to remove them.
The following packages will be REMOVED:
  mysql-server* mysql-server-5.7*
0 to upgrade, 0 to newly install, 2 to remove and 2 not to upgrade.
2 not fully installed or removed.
After this operation, 48.5 MB disk space will be freed.
Do you want to continue? [Y/n] Y
(Reading database ... 335892 files and directories currently installed.)
Removing mysql-server (5.7.12-0ubuntu1) ...
Removing mysql-server-5.7 (5.7.12-0ubuntu1) ...
update-alternatives: warning: alternative /etc/mysql/my.cnf.fallback (part of link group my.cnf) doesn't exist; removing from list of alternatives
update-alternatives: warning: alternative /etc/mysql/my.cnf.migrated (part of link group my.cnf) doesn't exist; removing from list of alternatives
update-alternatives: warning: alternative /etc/mysql/mysql.cnf (part of link group my.cnf) doesn't exist; removing from list of alternatives
update-alternatives: warning: /etc/alternatives/my.cnf is dangling; it will be updated with best choice
Purging configuration files for mysql-server-5.7 (5.7.12-0ubuntu1) ...
Processing triggers for man-db (2.7.5-1) ...

:~$ sudo apt-get install mysql-server
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following additional packages will be installed:
  mysql-server-5.7
Suggested packages:
  tinyca
The following NEW packages will be installed:
  mysql-server mysql-server-5.7
0 to upgrade, 2 to newly install, 0 to remove and 2 not to upgrade.
Need to get 0 B/2,594 kB of archives.
After this operation, 48.5 MB of additional disk space will be used.
Do you want to continue? [Y/n] Y
Preconfiguring packages ...
Selecting previously unselected package mysql-server-5.7.
(Reading database ... 335805 files and directories currently installed.)
Preparing to unpack .../mysql-server-5.7_5.7.12-0ubuntu1_amd64.deb ...
grep: /etc/mysql/: No such file or directory
Unpacking mysql-server-5.7 (5.7.12-0ubuntu1) ...
Selecting previously unselected package mysql-server.
Preparing to unpack .../mysql-server_5.7.12-0ubuntu1_all.deb ...
Unpacking mysql-server (5.7.12-0ubuntu1) ...
Processing triggers for systemd (229-4ubuntu4) ...
Processing triggers for ureadahead (0.100.0-19) ...
Processing triggers for man-db (2.7.5-1) ...
Setting up mysql-server-5.7 (5.7.12-0ubuntu1) ...
update-alternatives: using /etc/mysql/mysql.cnf to provide /etc/mysql/my.cnf (my.cnf) in auto mode
Job for mysql.service failed because the control process exited with error code. See "systemctl status mysql.service" and "journalctl -xe" for details.
invoke-rc.d: initscript mysql, action "start" failed.
dpkg: error processing package mysql-server-5.7 (--configure):
 subprocess installed post-installation script returned error exit status 1
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
No apport report written because the error message indicates its a followup error from a previous failure.
                                                                                                          Processing triggers for systemd (229-4ubuntu4) ...
Processing triggers for ureadahead (0.100.0-19) ...
Errors were encountered while processing:
 mysql-server-5.7
 mysql-server
E: Sub-process /usr/bin/dpkg returned an error code (1)