PHP Fatal error: Class 't3lib_extMgm' not found in D:\htdocs\provida.marty.local\public_html\typo3conf\ext\jfmulticontent\ext_tables.php on line 186

[marcelmarty]

Change line 186 in ext_tables.php, because loading error in TYPO3 7.6

OLD:
$TBE_MODULES_EXT['xMOD_db_new_content_el']['addElClasses']['tx_jfmulticontent_pi1_wizicon'] = t3lib_extMgm::extPath($_EXTKEY) . 'pi1/class.tx_jfmulticontent_pi1_wizicon.php';

NEW:
$TBE_MODULES_EXT['xMOD_db_new_content_el']['addElClasses']['tx_jfmulticontent_pi1_wizicon'] = \TYPO3\CMS\Core\Utility\ExtensionManagementUtility::extPath($_EXTKEY) . 'pi1/class.tx_jfmulticontent_pi1_wizicon.php';

[cedricziel]

We just removed it from all of our instances. You can send a pull-request if you like.