title: liquibase gradle plugin can not find org.postgresql.Driver
body: <p>I am trying to use <a href="https://github.com/liquibase/liquibase-gradle-plugin" rel="nofollow noreferrer">liquibase-gradle-plugin</a> to generate database diffs between a database and Springboot Entities. However, I always got the error saying  </p>
  
  <blockquote>
    <p>liquibase.exception.LiquibaseException: Unexpected error running Liquibase: java.lang.RuntimeException: Cannot find database driver: class org.postgresql.Driver</p>
  </blockquote>
  
  <p>I put classpath depencies in the buildscripts block according to some google result. But it does not help. Below is my build.gradle</p>
  
  <pre><code>buildscript {
      ext {
          springBootVersion = '1.5.6.RELEASE'
      }
      repositories {
          mavenCentral()
          maven { url "https://repo.spring.io/milestone" }
          maven {
              url "https://plugins.gradle.org/m2/"
            }
      }
      dependencies {
          classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
          classpath('org.postgresql:postgresql:9.4.1212')
      }
  }
  
  //When the liquibase plugin is applied, it creates a Gradle task for each command supported by Liquibase.
  plugins {
      id 'org.liquibase.gradle' version '1.2.4'
  }
  
  apply from: 'liquibase.gradle'
  
  liquibase {
      activities {
        diffMain {
          url gradle.ext.url
          username gradle.ext.username
          password gradle.ext.password
          referenceUrl gradle.ext.referenceUrl
          driver org.postgresql.Driver
        }
      }
      runList = 'diffMain'
  }
  </code></pre>