Print the traceback if there was an exception in run()

In case run() method fails, all we get is a terse "Unable to run Guru
Meditation Report!" message on stderr.

This patch also prints the traceback for easier debugging in the
unlikely event that GMR fails.

Change-Id: I99d4e0f1ed3ea608aa285f34314339b0939c5651

oslo_reports/guru_meditation_report.py

@@ -64,6 +64,7 @@ import logging
 import os
 import signal
 import sys
+import traceback
 
 from oslo_utils import timeutils
 
@@ -178,6 +179,7 @@ class GuruMeditation(object):
         try:
             res = cls(version, frame).run()
         except Exception:
+            traceback.print_exc(file=sys.stderr)
             print("Unable to run Guru Meditation Report!",
                   file=sys.stderr)
         else:

oslo_reports/tests/test_guru_meditation_report.py

@@ -180,6 +180,19 @@ class TestGuruMeditationReport(base.BaseTestCase):
                 log_dir, "fake-service_gurumeditation_20140101120000")) as df:
             self.assertIn('Guru Meditation', df.read())
 
+    @mock.patch.object(gmr.TextGuruMeditation, 'run')
+    def test_fail_prints_traceback(self, run_mock):
+        class RunFail(Exception):
+            pass
+
+        run_mock.side_effect = RunFail()
+        gmr.TextGuruMeditation.setup_autorun(FakeVersionObj())
+        self.old_stderr = sys.stderr
+        sys.stderr = six.StringIO()
+
+        os.kill(os.getpid(), signal.SIGUSR2)
+        self.assertIn('RunFail', sys.stderr.getvalue())
+
     def tearDown(self):
         super(TestGuruMeditationReport, self).tearDown()
         if self.old_stderr is not None: