[IMP] tests:

[IMP] tests:
- pass around the assertion_report to the YAML importer
- removed TestReport, which was identical to assertion_report
- assertion_report is simpler (no more severity level)
- use the report to log a greppable sentence when some test failed.
Previously the runbot had to grep for a Traceback which was an
unreliable technique (e.g. an exception can be purposefuly
generated as part of a test and the associated traceback
visible in the logs). Now it can grep
  "At least one test failed when loading the modules".

bzr revid: vmt@openerp.com-20120302110227-nqrl7i46ju28ntdr