Unable to start/stop server: permission problem

[Walter Griffith]

I am unable to start/stop the server in Workbench. When I try I get this:

Could not open error log file: [Errno 13] Permission denied: '/usr/local/mysql/data/mysqld.local.err'

Both mysqld.local.err and the data directory have 640 permission with
owner and group ids of _mysql. Changing the permissions on the log,
even to 777, doesn't seem to help. This started right after I installed
MySQL 5.7.11 (community edition) running on Mac OS X 10.9.5 and Workbench
6.3.6. Everything is 64-bit.

Larry Griffith