Use reload() from imp module

In Python 3 the reload() function [1] has been moved in the imp
module. [2]

[1] https://docs.python.org/2/library/functions.html#reload
[2] https://docs.python.org/3/library/importlib.html#importlib.reload

tests/__init__.py

@@ -28,7 +28,7 @@ os.environ["VIRTINST_TEST_URL_DIR"] = os.path.abspath(
 # pylint: disable=wrong-import-position
 from virtcli import cliconfig
 # This sets all the cli bits back to their defaults
-reload(cliconfig)
+imp.reload(cliconfig)
 
 from tests import utils