From: Matthew Vernon <mv3@sanger.ac.uk>
Date: Fri, 19 Oct 2018 11:41:54 +0000 (+0100)
Subject: only register gcal_link if necessary
X-Git-Tag: v0.1~16
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~matthewv/git?p=gooswapper;a=commitdiff_plain;h=3ab26f0d9fff9530325a1c227f4f2e8da81b6f58

only register gcal_link if necessary
---

diff --git a/gooswapper.py b/gooswapper.py
index f3c73a0..75edd3f 100644
--- a/gooswapper.py
+++ b/gooswapper.py
@@ -54,7 +54,10 @@ class ex_gcal_link(exchangelib.ExtendedProperty):
     property_name = "google calendar event id"
     property_type = 'String'
 
-exchangelib.CalendarItem.register('gcal_link',ex_gcal_link)
+try:
+    exchangelib.CalendarItem.get_field_by_fieldname('gcal_link')
+except ValueError:
+    exchangelib.CalendarItem.register('gcal_link',ex_gcal_link)
 
 #useful if you want to replay an event
 def drop_from_ex_cache(itemid):