Port more-robust shutdown_zeo_server() from Zope-2_7-branch.

src/ZEO/tests/forker.py

@@ -123,12 +123,23 @@ else:
 
 
 def shutdown_zeo_server(adminaddr):
+    # Do this in a loop to guard against the possibility that the
+    # client failed to connect to the adminaddr earlier.  That really
+    # only requires two iterations, but do a third for pure
+    # superstition.
+    for i in range(3):
         s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        try:
             s.connect(adminaddr)
+        except socket.error, e:
+            if e[0] == errno.ECONNREFUSED and i > 0:
+                break
+            raise
         try:
             ack = s.recv(1024)
         except socket.error, e:
-        if e[0] <> errno.ECONNRESET: raise
+            if e[0] == errno.ECONNRESET:
+                raise
             ack = 'no ack received'
         zLOG.LOG('shutdownServer', zLOG.DEBUG, 'acked: %s' % ack)
         s.close()