Raise error if unsupported charset for mysql

`blog$ bin/rails db:create`

Before:
```
Couldn't create database for {"adapter"=>"mysql2", "encoding"=>"utf42", "pool"=>5,
"username"=>"root", "password"=>nil, "socket"=>"/var/run/mysqld/mysqld.sock",
"database"=>"blog_development"}, {:charset=>"utf42"}
(If you set the charset manually, make sure you have a matching collation)
Created database 'blog_development'
Couldn't create database for {"adapter"=>"mysql2", "encoding"=>"utf42", "pool"=>5,
"username"=>"root", "password"=>nil, "socket"=>"/var/run/mysqld/mysqld.sock",
"database"=>"blog_test"}, {:charset=>"utf42"}
(If you set the charset manually, make sure you have a matching collation)
Created database 'blog_test'
```

After:
```
Unsupported charset: '"utf42"'
Couldn't create database for {"adapter"=>"mysql2", "encoding"=>"utf42", "pool"=>5,
"username"=>"root", "password"=>nil, "socket"=>"/var/run/mysqld/mysqld.sock",
"database"=>"blog_development"}
rails aborted!
Mysql2::Error: Unsupported charset: '"utf42"'
...
(stack trace)
...
bin/rails:4:in `<main>'
Tasks: TOP => db:create
(See full trace by running task with --trace)
```

Closes #29683
Related to #27398

1 files changed, 4 insertions, 4 deletions

diff --git a/activerecord/test/cases/tasks/mysql_rake_test.rb b/activerecord/test/cases/tasks/mysql_rake_test.rb
index 98fe24baa0..6c9b0040ad 100644
--- a/activerecord/test/cases/tasks/mysql_rake_test.rb
+++ b/activerecord/test/cases/tasks/mysql_rake_test.rb
@@ -156,12 +156,12 @@ if current_adapter?(:Mysql2Adapter)
         ActiveRecord::Tasks::DatabaseTasks.create @configuration
       end
 
-      def test_sends_output_to_stderr_when_other_errors
+      def test_raises_error_when_other_errors
         @error.stubs(:errno).returns(42)
 
-        $stderr.expects(:puts).at_least_once.returns(nil)
-
-        ActiveRecord::Tasks::DatabaseTasks.create @configuration
+        assert_raises(Mysql2::Error) do
+          ActiveRecord::Tasks::DatabaseTasks.create @configuration
+        end
       end
 
       private