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;
    }
  }
}

The Block Class module makes it possible to manually add classes through the block admin form. By default this feature is only compatible with blocks placed into block regions via the core user interface. This snippet makes it work for blocks placed into panels or mini panels as well (Panels module).

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);