Fix some more warnings from flake8

tests/rules/test_ssh_known_host.py

@@ -1,6 +1,5 @@
 import os
 import pytest
-from mock import Mock
 from thefuck.rules.ssh_known_hosts import match, get_new_command,\
     side_effect
 from tests.utils import Command

tests/rules/test_systemctl.py

@@ -1,4 +1,3 @@
-import pytest
 from thefuck.rules.systemctl import match, get_new_command
 from tests.utils import Command
 

tests/specific/test_sudo.py

@@ -1,5 +1,4 @@
 import pytest
-from mock import Mock
 from thefuck.specific.sudo import sudo_support
 from tests.utils import Command
 

tests/test_logs.py

@@ -1,5 +1,4 @@
 import pytest
-from mock import Mock
 from thefuck import logs
 
 

thefuck/specific/sudo.py

@@ -1,6 +1,5 @@
 import six
 from decorator import decorator
-from ..types import Command
 
 
 @decorator