Revert "[Autotest] Python3 files/server/* migration"

This reverts commit b05fb5a3dd205d085395c3e2f7d05127cabd07ec.

Reason for revert: Broke most WiFi server tests

Original change's description:
> [Autotest] Python3 files/server/* migration
> 
> Does not include subdirs
> TEST=applicable unittests, compiling in py2 and py3
> BUG=chromium:990593
> 
> Change-Id: I668c7531e7fc926f9a20c3bf2bab0d62eb3e3926
> Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/autotest/+/2318565
> Commit-Queue: Derek Beckett <dbeckett@chromium.org>
> Tested-by: Derek Beckett <dbeckett@chromium.org>
> Reviewed-by: Greg Edelston <gredelston@google.com>

Bug: chromium:990593
Change-Id: Ic50c342c09af9ed1852b8844a369b9629798bc0a
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/autotest/+/2370865
Reviewed-by: Nicolas Norvez <norvez@chromium.org>
Reviewed-by: Gregory Nisbet <gregorynisbet@google.com>
Reviewed-by: Fei Shao <fshao@chromium.org>
Commit-Queue: Nicolas Norvez <norvez@chromium.org>
Tested-by: Nicolas Norvez <norvez@chromium.org>
diff --git a/server/frontend.py b/server/frontend.py
index b0d8f97..fe942e0 100644
--- a/server/frontend.py
+++ b/server/frontend.py
@@ -1,4 +1,3 @@
-# Lint as: python2, python3
 # Copyright Martin J. Bligh, Google Inc 2008
 # Released under the GPL v2
 
@@ -16,10 +15,6 @@
 
 #pylint: disable=missing-docstring
 
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-
 import getpass
 import os
 import re
@@ -33,7 +28,6 @@
 from autotest_lib.client.common_lib import priorities
 from autotest_lib.client.common_lib import utils
 from autotest_lib.tko import db
-from six.moves import zip
 
 try:
     from chromite.lib import metrics
@@ -98,8 +92,8 @@
         headers = {'AUTHORIZATION': self.user}
         rpc_server = rpc_client_lib.add_protocol(server) + path
         if debug:
-            print('SERVER: %s' % rpc_server)
-            print('HEADERS: %s' % headers)
+            print 'SERVER: %s' % rpc_server
+            print 'HEADERS: %s' % headers
         self.proxy = rpc_client_lib.get_proxy(rpc_server, headers=headers)
 
 
@@ -109,11 +103,11 @@
         """
         rpc_call = getattr(self.proxy, call)
         if self.debug:
-            print('DEBUG: %s %s' % (call, dargs))
+            print 'DEBUG: %s %s' % (call, dargs)
         try:
             result = utils.strip_unicode(rpc_call(**dargs))
             if self.reply_debug:
-                print(result)
+                print result
             return result
         except Exception:
             raise
@@ -121,7 +115,7 @@
 
     def log(self, message):
         if self.print_log:
-            print(message)
+            print message
 
 
 class TKO(RpcClient):
@@ -873,9 +867,9 @@
 
     def show(self):
         labels = list(set(self.labels) - set([self.platform]))
-        print('%-6s %-7s %-7s %-16s %s' % (self.hostname, self.status,
+        print '%-6s %-7s %-7s %-16s %s' % (self.hostname, self.status,
                                            self.locked, self.platform,
-                                           ', '.join(labels)))
+                                           ', '.join(labels))
 
 
     def delete(self):