Add --verbose flag to recipe_config_test.py to print exception stack traces.
Add --verbose flag to recipe_config_test.py to print exception stack traces.

Without stack traces errors reported by recipe_configs_test are hard to debug
(especially considering an esoteric nature of config system).

Also make exceptions in config evaluation to fail the test.

Also fix a minor bug in v8 recipe module that went unnoticied because
config test failures were not counted as failures if coverage is at 100%.

R=iannucci@chromium.org
BUG=

Review URL: https://codereview.chromium.org/240573003

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@264673 0039d316-1c4b-4281-b951-d872f2087c98

luci/recipes-py,shishkander/recipes-py,shishkander/recipes-py,luci/recipes-py