cros_run_unit_tests: do not reraise final failure

When we run RunUnittests, it takes care of logging the full command
that it ran (the emerge & packages).  So there's no value in having
this main script rethrow the run command exception when the tests
failed.  We already logged an error, and the failure logs are shown
above pretty clearly.  This tightens up the failure scenario quite
a bit without losing any information for devs.

BUG=chromium:996480
TEST=`cros_run_unit_tests --board betty` looks a bit nicer when it fails

Change-Id: I55ed4f590f8edf17aca7166848e9f30bf3435b1a
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/1778714
Reviewed-by: Chris McDonald <cjmcdonald@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
diff --git a/scripts/cros_run_unit_tests.py b/scripts/cros_run_unit_tests.py
index cfecf47..fcf892d 100644
--- a/scripts/cros_run_unit_tests.py
+++ b/scripts/cros_run_unit_tests.py
@@ -133,11 +133,11 @@
                          use_binary=False)
     except cros_build_lib.RunCommandError:
       logging.error('Failed building dependencies for unittests.')
-      raise
+      return 1
 
   try:
     chroot_util.RunUnittests(sysroot, pkg_with_test, extra_env=env,
                              jobs=min(10, multiprocessing.cpu_count()))
   except cros_build_lib.RunCommandError:
     logging.error('Unittests failed.')
-    raise
+    return 1