Use lock with 'with' statement

To make sure, the lock gets released even if we raise an exception between
acquire() and release()

Signed-off-by: Sebastian Spaeth <Sebastian@SSpaeth.de>

offlineimap/imapserver.py

@@ -15,6 +15,7 @@
 #    along with this program; if not, write to the Free Software
 #    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
 
+from __future__ import with_statement # needed for python 2.5
 from offlineimap import imaplibutil, imaputil, threadutil, OfflineImapError
 from offlineimap.ui import getglobalui
 from threading import Lock, BoundedSemaphore, Thread, Event, currentThread
@@ -370,7 +371,8 @@ class IMAPServer:
     def close(self):
         # Make sure I own all the semaphores.  Let the threads finish
         # their stuff.  This is a blocking method.
-        self.connectionlock.acquire()
+        with self.connectionlock:
+            # first, wait till all
             threadutil.semaphorereset(self.semaphore, self.maxconnections)
             for imapobj in self.assignedconnections + self.availableconnections:
                 imapobj.logout()
@@ -381,7 +383,6 @@ class IMAPServer:
             self.gss_step = self.GSS_STATE_STEP
             self.gss_vc = None
             self.gssapi = False
-        self.connectionlock.release()
 
     def keepalive(self, timeout, event):
         """Sends a NOOP to each connection recorded.   It will wait a maximum