View source for MyRoundcube Calendar Plugin external calendars issues (CalDAV)

'''Problem:'''
* MyRoundcube Calendar Plugin is not able to load external calendars which require username and password authentication.
* Adding a new CalDAV calendar gives the following error message:
 ''Failed to save changes.''<br>
 ''Failed to establish connection. Please check your data.''
* Roundcube setup:
** Roundcube 1.0.4
** calendar 19.0.49
** calendar_plus 4.0.37
** PHP 5.4.34
** MySQL 5.5.40

'''Solution:'''
* Issue might be the PHP variable '''open_basedir''' which is set.
* Either remove open_basedir, or change '''CURLOPT_FOLLOWLOCATION''' to '''false''' in the corresponding PHP file(s). In this case ''SabreDAV/lib/Sabre/DAV/Client.php'':
 326: CURLOPT_FOLLOWLOCATION => false,

'''Note:'''
* For more details, see [https://forum.myroundcube.com/topic/249-connection-error-calendar-and-owncloud-caldav-backend/], [https://forum.myroundcube.com/topic/248-open-basedir-with-caldav/] and [https://forum.myroundcube.com/topic/223-connection-error-calendar-19042/].