Current behavior
Currently, Team Calendar gadget cannot be viewed in Jira

Step to reproduce:
In Jira, "Add Gadget" --> "Confluence Page Gadget", addressing space a page and save. The result is the following error message:

Error rendering macro 'calendar' : No enum constant com.atlassian.confluence.content.render.xhtml.ConversionContextOutputType.PAGE_GADGET

and the following error message on the logs:

2012-10-26 12:52:48,875 ERROR [http-10432-1] [xhtml.view.macro.ViewMacroMarshaller] marshal Error rendering macro: calendar
 -- url: /rest/gadget/1.0/pagegadget/getrenderedpage.json | userName: admin
java.lang.IllegalArgumentException: No enum const class com.atlassian.confluence.content.render.xhtml.ConversionContextOutputType.PAGE_GADGET

Reason that this is happening
Team Calendars for Confluence macro is not currently compatible with the JIRA Page Gadget. This is explained here:

• Cannot Display a Confluence page with a Team Calendars for Confluence macro in a JIRA Page Gadget
• Make Team Calendars display in a Confluence Page Gadget, for use on a JIRA Dashboard

Desired behavior:
The error message is displaying something that's definitively an admin should not do, a human-readable error, such as
"Oops, Jira is not compatible with Team Calendars for Confluence gadget and therefore cannot display it"