从您共享的database.yml和发布的日志来看，似乎无法找到数据库所在的路径。
将database.yml更改为

default: &default
  adapter: mysql2
  pool: 5
  encoding: utf8
  min_messages: warning
  timeout: 5000
  username: root
  password:
  database: heart_development
  host: localhost

数据库必须连接到的指定主机。

我评论了环境变量 DATABASE_URL 在我的 .env 文件。我还配置了 database.yml 接下来：

development:
  adapter: mysql2
  encoding: utf8
  reconnect: false
  database: heart_development
  pool: 5
  username: root
  password:
  host: localhost
  port: 3306

test:
  adapter: mysql2
  encoding: utf8
  reconnect: false
  database: heart_test
  pool: 5
  username: root
  password:
  host: localhost
  port: 3306

production:
  adapter: mysql2
  encoding: utf8cm
  reconnect: false
  database: heart_production
  pool: 5
  username: root
  password:
  host: localhost
  port: 3306