Error:
/Users/askar/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/mysql2-0.3.20/lib/mysql2.rb:31:in `require': dlopen(/Users/askar/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/extensions/x86_64-darwin-14/2.2.0-static/mysql2-0.3.20/mysql2/mysql2.bundle, 9): Library not loaded: /usr/local/lib/libmysqlclient.18.dylib (LoadError)
Referenced from: /Users/askar/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/extensions/x86_64-darwin-14/2.2.0-static/mysql2-0.3.20/mysql2/mysql2.bundle
Reason: image not found - /Users/askar/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/extensions/x86_64-darwin-14/2.2.0-static/mysql2-0.3.20/mysql2/mysql2.bundle
In Gemfile: gem 'mysql2'
$ ls -al /usr/local/lib/libmysql*
lrwxr-xr-x 1 askar admin 49 Nov 13 10:48 /usr/local/lib/libmysqlclient.20.dylib -> ../Cellar/mysql/5.7.9/lib/libmysqlclient.20.dylib
lrwxr-xr-x 1 askar admin 42 Nov 13 10:48 /usr/local/lib/libmysqlclient.a -> ../Cellar/mysql/5.7.9/lib/libmysqlclient.a
lrwxr-xr-x 1 askar admin 46 Nov 13 10:48 /usr/local/lib/libmysqlclient.dylib -> ../Cellar/mysql/5.7.9/lib/libmysqlclient.dylib
lrwxr-xr-x 1 askar admin 37 Nov 13 10:48 /usr/local/lib/libmysqld.a -> ../Cellar/mysql/5.7.9/lib/libmysqld.a
lrwxr-xr-x 1 askar admin 44 Nov 13 10:48 /usr/local/lib/libmysqlservices.a -> ../Cellar/mysql/5.7.9/lib/libmysqlservices.a
$ ls -al /usr/local/Cellar/mysql/5.7.9/lib/
total 84392
drwxr-xr-x 9 askar admin 306 Nov 12 22:16 .
drwxr-xr-x 14 askar admin 476 Nov 13 10:48 ..
-r--r--r-- 1 askar admin 3780168 Nov 13 10:48 libmysqlclient.20.dylib
-r--r--r-- 1 askar admin 4280752 Nov 12 22:16 libmysqlclient.a
lrwxr-xr-x 1 askar admin 23 Nov 12 22:16 libmysqlclient.dylib -> libmysqlclient.20.dylib
-r--r--r-- 1 askar admin 35126528 Nov 12 22:16 libmysqld.a
-r--r--r-- 1 askar admin 9048 Nov 12 22:16 libmysqlservices.a
drwxr-xr-x 3 askar admin 102 Nov 13 10:48 pkgconfig
drwxr-xr-x 43 askar admin 1462 Nov 12 22:17 plugin
drwxr-xr-x 43 askar admin 1462 Nov 12 22:17 plugin
As you see I'm having libmysqlclient.20.dylib, it's 20 not 18, otherwise I'd follow the solution here.
I've recently upgraded to El Capitan but not sure it that's the cause.
UPDATE:
Thanks to @Rashmirathi for the hint to re-install the gem.
Just wanted to note, I needed also to specify in Gemfile as:
gem 'mysql2', '~> 0.3.18'
Otherwise I had error:
Specified 'mysql2' for database adapter, but the gem is not loaded. Add
gem 'mysql2'to your Gemfile (and ensure its version is at the minimum required by ActiveRecord).
But finally I got error:
Mysql2::Error
Your password has expired. To log in you must change it using a client that supports expired passwords.
Which is solved by setting up a password again:
SET PASSWORD=PASSWORD('your_password');