Add block_class classes to panel pane markup

template.php

<?php
/**
 * Modify panels pane template variables
 */
function MYTHEME_preprocess_panels_pane(&$variables) {
  // Merge block_class classes into the pane's $classes_array
  if (module_exists('block_class')) {
    // Insert additional classes into panels panes.
    if ($variables['pane']->type == 'block') {
      // Infer the block's $module and $delta from the pane subtype.
      $block_parts = explode('-', $variables['pane']->subtype);
      // Load the block based on the block parts.
      $block = block_load($block_parts[0], $block_parts[1]);
      // Return block_class classes as string.
      $css_class = block_class($block);
      // Add a generic module type block class.
      $variables['classes_array'][] = drupal_html_class('pane-' . $block->module);
      // Add $css_class to the $classes_array.
      $variables['classes_array'][] = $css_class;
    }
  }
}

I found that this fails if the delta of the module contains a "-", like in blocks generated by Views.
I fixed it replacing line 13 with the following:

  $module = array_shift($block_parts);
  $delta = implode('-', $block_parts);
  $block = block_load($module, $delta);