runUnitTest: display actual error when running a test component with error

Instead of displaying the same ImportError without any detail for both
cases of a non existant module or of an existing module which cause
error during import, improve the second case by displaying a different
message containing the original traceback.
30 jobs for DateTime.equalTo_fix in 0 seconds
Status Job ID Name Coverage
  External
failed ERP5.CodingStyleTest-TestRunner1

01:28:37

passed ERP5.PerformanceTest-TestRunner1

00:27:22

failed ERP5.UnitTest-TestRunner1

03:11:59

failed ERP5.UnitTest-Zope2-ForTestRunner1

02:08:32

failed ERP5.CodingStyleTest-TestRunner1

01:30:28

passed ERP5.PerformanceTest-TestRunner1

00:27:20

failed ERP5.UnitTest-TestRunner1

08:33:54

failed ERP5.UnitTest-TestRunner1

03:29:58

failed ERP5.UnitTest-TestRunner1

04:14:42

failed ERP5.UnitTest-TestRunner1

02:30:43

failed ERP5.UnitTest-TestRunner1

04:13:26

failed ERP5.UnitTest-TestRunner1

02:49:40

failed ERP5.UnitTest-TestRunner1

03:38:38

failed ERP5.UnitTest-TestRunner1

03:43:51

failed ERP5.UnitTest-TestRunner1

04:04:38

failed ERP5.UnitTest-TestRunner1

03:07:44

failed ERP5.UnitTest-TestRunner1

05:12:24

failed ERP5.UnitTest-TestRunner1

03:00:05

failed ERP5.UnitTest-Zope2-ForTestRunner1

01:57:01

failed ERP5.UnitTest-Zope2-ForTestRunner1

02:18:08

failed ERP5.UnitTest-Zope2-ForTestRunner1

04:01:32

failed ERP5.UnitTest-Zope2-ForTestRunner1

01:57:48

failed ERP5.UnitTest-Zope2-ForTestRunner1

03:46:07

failed ERP5.UnitTest-Zope2-ForTestRunner1

02:48:54

failed ERP5.UnitTest-Zope2-ForTestRunner1

02:28:19

failed ERP5.UnitTest-Zope2-ForTestRunner1

07:17:10

failed ERP5.UnitTest-Zope2-ForTestRunner1

03:47:17

failed ERP5.UnitTest-Zope2-ForTestRunner1

02:12:58

failed ERP5.UnitTest-Zope2-ForTestRunner1

02:05:12

failed ERP5.UnitTest-Zope2-ForTestRunner1

02:18:02