Problems starting MySQL

Using MySQL 14.14 distrib 5.7.9 for osx10.11 on El Capitan 10.11.3

An existing MySQL database suddenly stopped running after a restart. When I tried to connect I first got this error:

Can't connect to local MySQL server through socket '/tmp/mysql.sock' (2)

So tried to run mysql.server start and got this error:

ERROR! The server quit without updating PID file (/usr/local/var/mysql/Honshu.local.pid)

Tried using sudo but that did not change anything.

Went to install location and removed the *.err file (which was 53Mb!?)

sudo rm /usr/local/var/mysql/Honshu.local.err

Then ran mysql.server start and it started up just fine.