[PATCH 4/6] Add check for IDLE in capabilities

[Ethan Glasser-Camp]

If the server doesn't support IDLE, we fall back to the standard
noop() keepalive.

This commit was originally by James Bunton <jamesbunton at fastmail.fm>.

Signed-off-by: Ethan Glasser-Camp <ethan at betacantrips.com>
---
 offlineimap/imapserver.py |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/offlineimap/imapserver.py b/offlineimap/imapserver.py
index e5613fb..889daa3 100644
--- a/offlineimap/imapserver.py
+++ b/offlineimap/imapserver.py
@@ -411,7 +411,13 @@ class IdleThread(object):
                     self.event.set()
             imapobj = self.parent.acquireconnection()
             imapobj.select(self.folder)
-            imapobj.idle(callback=callback)
+            if "IDLE" in imapobj.capabilities:
+                imapobj.idle(callback=callback)
+            else:
+                self.ui = getglobalui()
+                ui.warn("IMAP IDLE not supported on connection to %s; falling back to no-op"
+                        %(imapobj.identifier,))
+                imapobj.noop()
             self.event.wait()
             if self.event.isSet():
                 imapobj.noop()
-- 
1.7.4.1