ENH: also print the failing traceback line in case of failure

Also to troubleshoot
https://travis-ci.org/fail2ban/fail2ban/jobs/7112324

testcases/misctestcase.py

@@ -133,8 +133,8 @@ class TestsUtilsTest(unittest.TestCase):
 				print deep_function(3)
 			except ValueError:
 				s = tb()
-			self.assertFalse('>' in s)  # There is only "fail2ban-testcases" in this case, no true traceback
+			self.assertFalse('>' in s, msg="'>' present in %r" % s)  # There is only "fail2ban-testcases" in this case, no true traceback
-			self.assertTrue(':' in s)
+			self.assertTrue(':' in s, msg="no ':' in %r" % s)
 
 
 	def testFormatterWithTraceBack(self):