update examples/simple/client.py and server.py to work with Python3
diff --git a/examples/simple/server.py b/examples/simple/server.py
index 37e36dd..539e773 100644
--- a/examples/simple/server.py
+++ b/examples/simple/server.py
@@ -14,11 +14,11 @@
 
 def verify_cb(conn, cert, errnum, depth, ok):
     # This obviously has to be updated
-    print 'Got certificate: %s' % cert.get_subject()
+    print('Got certificate: %s' % cert.get_subject())
     return ok
 
 if len(sys.argv) < 2:
-    print 'Usage: python[2] server.py PORT'
+    print('Usage: python[2] server.py PORT')
     sys.exit(1)
 
 dir = os.path.dirname(sys.argv[0])
@@ -44,12 +44,12 @@
 
 def dropClient(cli, errors=None):
     if errors:
-        print 'Client %s left unexpectedly:' % (clients[cli],)
-        print '  ', errors
+        print('Client %s left unexpectedly:' % (clients[cli],))
+        print('  ', errors)
     else:
-        print 'Client %s left politely' % (clients[cli],)
+        print('Client %s left politely' % (clients[cli],))
     del clients[cli]
-    if writers.has_key(cli):
+    if cli in writers:
         del writers[cli]
     if not errors:
         cli.shutdown()
@@ -57,14 +57,14 @@
 
 while 1:
     try:
-        r,w,_ = select.select([server]+clients.keys(), writers.keys(), [])
+        r,w,_ = select.select([server]+list(clients.keys()), list(writers.keys()), [])
     except:
         break
 
     for cli in r:
         if cli == server:
             cli,addr = server.accept()
-            print 'Connection from %s' % (addr,)
+            print('Connection from %s' % (addr,))
             clients[cli] = addr
 
         else:
@@ -74,10 +74,10 @@
                 pass
             except SSL.ZeroReturnError:
                 dropClient(cli)
-            except SSL.Error, errors:
+            except SSL.Error as errors:
                 dropClient(cli, errors)
             else:
-                if not writers.has_key(cli):
+                if cli not in writers:
                     writers[cli] = ''
                 writers[cli] = writers[cli] + ret
 
@@ -88,13 +88,13 @@
             pass
         except SSL.ZeroReturnError:
             dropClient(cli)
-        except SSL.Error, errors:
+        except SSL.Error as errors:
             dropClient(cli, errors)
         else:
             writers[cli] = writers[cli][ret:]
             if writers[cli] == '':
                 del writers[cli]
 
-for cli in clients.keys():
+for cli in list(clients.keys()):
     cli.close()
 server.close()