client: close failing connection explicitly in case of unhandled exception

The changes consist in:
- indenting many lines without exceeding 80 chars
- setting conn = None ASAP on ConnectionClosed
- adding a try..except clause

Starting from next commit, the exception can be POSException.ReadOnlyError.

neo/client/app.py

@@ -200,6 +200,8 @@ class Application(ThreadedApplication):
         fail_count = 0
         ask = self._ask
         handler = self.primary_bootstrap_handler
+        conn = None
+        try:
             while 1:
                 self.ignore_invalidations = True
                 # Get network connection to primary master
@@ -213,10 +215,10 @@ class Application(ThreadedApplication):
                         # Otherwise, check one by one.
                         master_list = self.nm.getMasterList()
                         if not master_list:
-                        # XXX: On shutdown, it already happened that this list
-                        #      is empty, leading to ZeroDivisionError. This
-                        #      looks a minor issue so let's wait to have more
-                        #      information.
+                            # XXX: On shutdown, it already happened that this
+                            #      list is empty, leading to ZeroDivisionError.
+                            #      This looks a minor issue so let's wait to
+                            #      have more information.
                             logging.error('%r', self.__dict__)
                         index = (index + 1) % len(master_list)
                         node = master_list[index]
@@ -230,6 +232,7 @@ class Application(ThreadedApplication):
                     try:
                         ask(conn, p, handler=handler)
                     except ConnectionClosed:
+                        conn = None
                         fail_count += 1
                     else:
                         self.primary_master_node = node
@@ -247,9 +250,14 @@ class Application(ThreadedApplication):
                     if self.pt.operational():
                         break
                 except ConnectionClosed:
-                logging.error('Connection to %s lost', self.trying_master_node)
-                self.primary_master_node = None
+                    conn = self.primary_master_node = None
+                    logging.error('Connection to %s lost',
+                                  self.trying_master_node)
                 fail_count += 1
+        except:
+            if conn is not None:
+                conn.close()
+            raise
         logging.info("Connected and ready")
         return conn