command: convert to python3 only

All users of this module are python3 only already.

BUG=chromium:997354
TEST=`./run_tests` passes

Change-Id: I68a77c49b0d470fd27d6e6b8e4ff15ae205a1898
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/2646227
Tested-by: Mike Frysinger <vapier@chromium.org>
Auto-Submit: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Alex Klein <saklein@chromium.org>
Reviewed-by: Alex Klein <saklein@chromium.org>
diff --git a/cli/command.py b/cli/command.py
index b756e77..f2d45e9 100644
--- a/cli/command.py
+++ b/cli/command.py
@@ -18,6 +18,7 @@
 
 import importlib
 import os
+import sys
 
 from chromite.lib import constants
 from chromite.lib import commandline
@@ -25,6 +26,9 @@
 from chromite.lib import cros_logging as logging
 
 
+assert sys.version_info >= (3, 6), 'This module requires Python 3.6+'
+
+
 # Paths for finding and importing subcommand modules.
 _SUBCOMMAND_MODULE_DIRECTORY = os.path.join(os.path.dirname(__file__), 'cros')
 _SUBCOMMAND_MODULE_PREFIX = 'cros_'
diff --git a/cli/command_unittest b/cli/command_unittest
deleted file mode 120000
index 72196ce..0000000
--- a/cli/command_unittest
+++ /dev/null
@@ -1 +0,0 @@
-../scripts/wrapper.py
\ No newline at end of file
diff --git a/cli/command_unittest.py b/cli/command_unittest.py
index 09a594f..6fec67f 100644
--- a/cli/command_unittest.py
+++ b/cli/command_unittest.py
@@ -10,6 +10,7 @@
 import argparse
 import importlib
 import os
+import sys
 
 from chromite.cli import command
 from chromite.lib import commandline
@@ -17,6 +18,9 @@
 from chromite.lib import partial_mock
 
 
+assert sys.version_info >= (3, 6), 'This module requires Python 3.6+'
+
+
 # pylint:disable=protected-access
 
 _COMMAND_NAME = 'superAwesomeCommandOfFunness'
diff --git a/lib/commandline_unittest b/lib/commandline_unittest
deleted file mode 120000
index 72196ce..0000000
--- a/lib/commandline_unittest
+++ /dev/null
@@ -1 +0,0 @@
-../scripts/wrapper.py
\ No newline at end of file