cloud_trace: convert to python3 only

All users of this module are python3 only already.

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

Change-Id: I273a593676e338150b574b539d897cf5b2d085c0
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/2643341
Tested-by: Mike Frysinger <vapier@chromium.org>
Auto-Submit: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Michael Mortensen <mmortensen@google.com>
Commit-Queue: Michael Mortensen <mmortensen@google.com>
diff --git a/lib/cloud_trace.py b/lib/cloud_trace.py
index 944a14b..02144fa 100644
--- a/lib/cloud_trace.py
+++ b/lib/cloud_trace.py
@@ -13,6 +13,7 @@
 import os
 import random
 import re
+import sys
 
 import google.protobuf.internal.well_known_types as types
 from infra_libs import ts_mon
@@ -22,6 +23,9 @@
 from chromite.lib import structured
 
 
+assert sys.version_info >= (3, 6), 'This module requires Python 3.6+'
+
+
 SPANS_LOG = '/var/log/trace/{pid}-{span_id}.json'
 _SPAN_COUNT_METRIC = 'chromeos/trace/client/logged_count'
 
diff --git a/lib/cloud_trace_unittest b/lib/cloud_trace_unittest
deleted file mode 120000
index 72196ce..0000000
--- a/lib/cloud_trace_unittest
+++ /dev/null
@@ -1 +0,0 @@
-../scripts/wrapper.py
\ No newline at end of file
diff --git a/lib/cloud_trace_unittest.py b/lib/cloud_trace_unittest.py
index 6627cf9..cdb3e4a 100644
--- a/lib/cloud_trace_unittest.py
+++ b/lib/cloud_trace_unittest.py
@@ -7,11 +7,15 @@
 from __future__ import print_function
 
 import os
+import sys
 
 from chromite.lib import cloud_trace
 from chromite.lib import cros_test_lib
 
 
+assert sys.version_info >= (3, 6), 'This module requires Python 3.6+'
+
+
 class SpanTest(cros_test_lib.MockTestCase):
   """Tests for the Span class."""