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/subcommand.py b/server/subcommand.py
index 234c81a..95053d1 100644
--- a/server/subcommand.py
+++ b/server/subcommand.py
@@ -1,15 +1,9 @@
-# Lint as: python2, python3
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-
 __author__ = """Copyright Andy Whitcroft, Martin J. Bligh - 2006, 2007"""
 
-import sys, os, signal, time, six.moves.cPickle, logging
+import sys, os, signal, time, cPickle, logging
 
 from autotest_lib.client.common_lib import error, utils
 from autotest_lib.client.common_lib.cros import retry
-from six.moves import zip
 
 
 # entry points that use subcommand must set this to their logging manager
@@ -47,7 +41,7 @@
             if status != 0:
                 run_error = True
 
-        results.append(six.moves.cPickle.load(task.result_pickle))
+        results.append(cPickle.load(task.result_pickle))
         task.result_pickle.close()
 
     if return_results:
@@ -97,7 +91,7 @@
         if return_results:
             try:
                 result = function(arg)
-            except Exception as e:
+            except Exception, e:
                 return [e]
             return [result]
         else:
@@ -184,12 +178,12 @@
             for hook in self.fork_hooks:
                 hook(self)
             result = self.func(*self.args)
-            os.write(w, six.moves.cPickle.dumps(result, six.moves.cPickle.HIGHEST_PROTOCOL))
+            os.write(w, cPickle.dumps(result, cPickle.HIGHEST_PROTOCOL))
             exit_code = 0
-        except Exception as e:
+        except Exception, e:
             logging.exception('function failed')
             exit_code = 1
-            os.write(w, six.moves.cPickle.dumps(e, six.moves.cPickle.HIGHEST_PROTOCOL))
+            os.write(w, cPickle.dumps(e, cPickle.HIGHEST_PROTOCOL))
 
         os.close(w)
 
@@ -215,16 +209,16 @@
             raise RuntimeError("Unknown child exit status!")
 
         if self.returncode != 0:
-            print("subcommand failed pid %d" % self.pid)
-            print("%s" % (self.func,))
-            print("rc=%d" % self.returncode)
-            print()
+            print "subcommand failed pid %d" % self.pid
+            print "%s" % (self.func,)
+            print "rc=%d" % self.returncode
+            print
             if self.debug:
                 stderr_file = os.path.join(self.debug, 'autoserv.stderr')
                 if os.path.exists(stderr_file):
                     for line in open(stderr_file).readlines():
-                        print(line, end=' ')
-            print("\n--------------------------------------------\n")
+                        print line,
+            print "\n--------------------------------------------\n"
             raise error.AutoservSubcommandError(self.func, self.returncode)
 
 
@@ -260,10 +254,10 @@
 
             if result is None:
                 utils.nuke_pid(self.pid)
-                print("subcommand failed pid %d" % self.pid)
-                print("%s" % (self.func,))
-                print("timeout after %ds" % timeout)
-                print()
+                print "subcommand failed pid %d" % self.pid
+                print "%s" % (self.func,)
+                print "timeout after %ds" % timeout
+                print
                 result = self.wait()
 
             return result