selftests/functional/test_standalone.py: adapt to Python 3 exceptions

Which includes the module name, and the different treatment of
exceptions that do not inherit from BaseExcpetion.
Signed-off-by: NCleber Rosa <crosa@redhat.com>

selftests/functional/test_standalone.py

 import os
+import sys
 import unittest
 
 from avocado.core import exit_codes
@@ -45,6 +46,9 @@ class StandaloneTests(unittest.TestCase):
         cmd_line = './examples/tests/errortest_nasty.py -r'
         expected_rc = exit_codes.AVOCADO_TESTS_FAIL
         result = self.run_and_check(cmd_line, expected_rc, 'errortest_nasty')
+        if sys.version_info[0] == 3:
+            exc = "errortest_nasty.NastyException: Nasty-string-like-exception"
+        else:
             exc = "NastyException: Nasty-string-like-exception"
         count = result.stdout.count("\n%s" % exc)
         self.assertEqual(count, 2, "Exception \\n%s should be present twice in"
@@ -62,8 +66,11 @@ class StandaloneTests(unittest.TestCase):
         cmd_line = './examples/tests/errortest_nasty3.py -r'
         expected_rc = exit_codes.AVOCADO_TESTS_FAIL
         result = self.run_and_check(cmd_line, expected_rc, 'errortest_nasty3')
-        self.assertIn("TestError: <errortest_nasty3.NastyException instance at ",
-                      result.stdout)
+        if sys.version_info[0] == 3:
+            exc = "TypeError: exceptions must derive from BaseException"
+        else:
+            exc = "TestError: <errortest_nasty3.NastyException instance at "
+        self.assertIn(exc, result.stdout)
 
     def test_errortest(self):
         cmd_line = './examples/tests/errortest.py -r'