gchar* vortex_frame_get_error_message gchar *  code,
gchar *  error_content,
gchar *  xml_lang

Creates and return the error message.

Allows to create a new error message that should be unrefered when no longer is needed.

code The error code to report.
error_content The error content, actually the textual error diagnostic.
xml_lang The language used to define the diagnostic message.
A newly allocated error message.