mibios/views: fix exception type formatting in error log

exc_type is the class already (and not the exception instance) so just
get the __name__ attribute.

mibios/views.py

@@ -624,10 +624,9 @@ def close(self):
         exc_type, exc_value, exc_traceback = sys.exc_info()
         if exc_type is not None:
             log.error(
-                f'Export aborted! cause: {exc_type.__class__.__name__}: '
-                f'{exc_value} / full)\n'
-                f'A traceback follows.  If additionally a full traceback is'
-                f'printed to stdout/err, then this indicated a bug\nin mibios/'
+                f'Export aborted! cause: {exc_type.__name__}: {exc_value}\n'
+                f'A traceback follows.  If additionally a full traceback is '
+                f'printed to stdout/err, then this indicates a bug in mibios/'
                 f'glamr.  Absense of the extra stack trace indicates that WSGI'
                 f' aborted the export, possibly for client disconnection.'
             )