title: Warning: [object Object] is not a PostCSS plugin. GruntJS with autoprefixer
body: <p>I am trying to use PostCSS plugin autoprefixer with grunt. I have gone through many articles and Stackoverflow answers which were relevant but still I am getting &quot;Warning: [object Object] is not a PostCSS plugin Use --force to continue&quot;.</p>
  <pre><code>    grunt.initConfig({
          pkg: grunt.file.readJSON('package.json'),
          sass: {
              dist: {
                  files: {
                      'css/style.css' : 'scss/style.scss'
                  }
              }
          },
          watch: {
              css: {
                  files: '**/*.scss',
                  tasks: ['sass']
              }
          },
          postcss: {
              options: {
                  map: true,
                  processors: [
                      require('autoprefixer')()
                  ]
              },
              dist: {
                  src: 'css/*.css'
              }
          }
      });
      grunt.loadNpmTasks('grunt-contrib-sass');
      grunt.loadNpmTasks('grunt-contrib-watch');
      grunt.loadNpmTasks('grunt-postcss');
      grunt.registerTask('dev',['sass','watch']);
      grunt.registerTask('build',['sass', 'postcss']);
  }
  
  package.json
    &quot;devDependencies&quot;: {
      &quot;grunt&quot;: &quot;^1.4.0&quot;,
      &quot;grunt-contrib-sass&quot;: &quot;^2.0.0&quot;,
      &quot;grunt-contrib-watch&quot;: &quot;^1.1.0&quot;,
      &quot;grunt-postcss&quot;: &quot;^0.9.0&quot;,
      &quot;postcss&quot;: &quot;^8.3.0&quot;,
      &quot;autoprefixer&quot;: &quot;^10.2.6&quot;
    }
  
  
  I am a newbie so please help.
  </code></pre>