Implement clean CTRL-C termination

Previously, we would simply bail out in an ugly way, potentially leaving
temporary files around etc, or while writing status files. Hand SIGINT
and SIGTERM as an event to the Account class, and make that bail out
cleanly at predefined points. Stopping on ctrl-c can take a few seconds
(it will e.g. finish to transfer the ongoing message), but it will shut
down cleanly.

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

offlineimap/init.py

@@ -288,11 +288,6 @@ class OfflineImap:
 
         self.config is supposed to have been correctly initialized
         already."""
-        def sigterm_handler(signum, frame):
-            # die immediately
-            self.ui.terminate(errormsg="terminating...")
-        signal.signal(signal.SIGTERM, sigterm_handler)
-
         try:
             pidfd = open(self.config.getmetadatadir() + "/pid", "w")
             pidfd.write(str(os.getpid()) + "\n")
@@ -328,11 +323,19 @@ class OfflineImap:
                     accounts.Account.set_abort_event(self.config, 1)
                 elif sig == signal.SIGUSR2:
                     # tell each account to stop looping
+                    getglobalui().warn("Terminating after this sync...")
                     accounts.Account.set_abort_event(self.config, 2)
+                elif sig == signal.SIGTERM or sig == signal.SIGINT:
+                    # tell each account to ABORT ASAP (ctrl-c)
+                    getglobalui().warn("Terminating NOW (this may "\
+                                       "take a few seconds)...")
+                    accounts.Account.set_abort_event(self.config, 3)
 
             signal.signal(signal.SIGHUP,sig_handler)
             signal.signal(signal.SIGUSR1,sig_handler)
             signal.signal(signal.SIGUSR2,sig_handler)
+            signal.signal(signal.SIGTERM, sig_handler)
+            signal.signal(signal.SIGINT, sig_handler)
 
             #various initializations that need to be performed:
             offlineimap.mbnames.init(self.config, syncaccounts)
@@ -361,9 +364,6 @@ class OfflineImap:
                 t.start()
                 threadutil.exitnotifymonitorloop(threadutil.threadexited)
             self.ui.terminate()
-        except KeyboardInterrupt:
-            self.ui.terminate(1, errormsg = 'CTRL-C pressed, aborting...')
-            return
         except (SystemExit):
             raise
         except Exception, e: