avocado.test: Save test traceback in Test.traceback

If a traceback was generated while executing an
avocado test, save the text contents to the
traceback attribute. It can then be used by code
such as the xunit plugin, to store that info.
Signed-off-by: NLucas Meneghel Rodrigues <lmr@redhat.com>

avocado/test.py

@@ -100,6 +100,7 @@ class Test(unittest.TestCase):
         self.resultsdir = None
         self.status = None
         self.fail_reason = None
+        self.traceback = None
 
         self.time_elapsed = None
         unittest.TestCase.__init__(self)
@@ -198,15 +199,21 @@ class Test(unittest.TestCase):
         except exceptions.TestBaseException, detail:
             self.status = detail.status
             self.fail_reason = detail
+            exc_type, exc_value, exc_traceback = sys.exc_info()
+            self.traceback = traceback.print_exception(exc_type, exc_value,
+                                                       exc_traceback.tb_next)
         except AssertionError, detail:
             self.status = 'FAIL'
             self.fail_reason = detail
+            exc_type, exc_value, exc_traceback = sys.exc_info()
+            self.traceback = traceback.print_exception(exc_type, exc_value,
+                                                       exc_traceback.tb_next)
         except Exception, detail:
             exc_type, exc_value, exc_traceback = sys.exc_info()
             tb_info = traceback.format_exception(exc_type, exc_value,
                                                  exc_traceback.tb_next)
-            tb_info = "".join(tb_info)
-            for e_line in tb_info.splitlines():
+            self.traceback = "".join(tb_info)
+            for e_line in tb_info:
                 self.log.error(e_line)
             self.status = 'FAIL'
             self.fail_reason = detail