Create sqlite3 directory if not present

If the `db/` directory is not present on a remote machine it will blow up in unexpected ways with error messages that do not indicate there is a missing directory:

```
SQLite3::CantOpenException: unable to open database file
```

This PR checks to see if a directory exists for the sqlite3 file and if not creates it for you.

This PR is an alternative to #11692 as suggested by @josevalim

activerecord/CHANGELOG.md

@@ -1,3 +1,7 @@
+*   Create a directory for sqlite3 file if not present on the system.
+
+    *Richard Schneeman*
+
 *   Removed redundant override of `xml` column definition for PG,
     in order to use `xml` column type instead of `text`.
 

activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb

@@ -17,12 +17,14 @@ module ActiveRecord
       # Allow database path relative to Rails.root, but only if
       # the database path is not the special path that tells
       # Sqlite to build a database only in memory.
-      if defined?(Rails.root) && ':memory:' != config[:database]
-        config[:database] = File.expand_path(config[:database], Rails.root)
+      if ':memory:' != config[:database]
+        config[:database] = Pathname.new(config[:database])
+        config[:database] = config[:database].expand_path(Rails.root) if defined?(Rails.root)
+        config[:database].dirname.mkdir unless config[:database].dirname.directory?
       end
 
       db = SQLite3::Database.new(
-        config[:database],
+        config[:database].to_s,
         :results_as_hash => true
       )
 

activerecord/test/cases/adapters/sqlite3/sqlite3_create_folder_test.rb

@@ -0,0 +1,21 @@
+# encoding: utf-8
+require "cases/helper"
+require 'models/owner'
+
+module ActiveRecord
+  module ConnectionAdapters
+    class SQLite3CreateFolder < ActiveRecord::TestCase
+      def test_sqlite_creates_directory
+        Dir.mktmpdir do |dir|
+          dir = Pathname.new(dir)
+          @conn = Base.sqlite3_connection :database => dir.join("db/foo.sqlite3"),
+                               :adapter => 'sqlite3',
+                               :timeout => 100
+
+          assert Dir.exists? dir.join('db')
+          assert File.exist? dir.join('db/foo.sqlite3')
+        end
+      end
+    end
+  end
+end